diff --git a/scripts/ssh/ssh-auth.php b/scripts/ssh/ssh-auth.php
--- a/scripts/ssh/ssh-auth.php
+++ b/scripts/ssh/ssh-auth.php
@@ -36,7 +36,7 @@
 
 $authstruct = null;
 
-if (strlen($authstruct_raw)) {
+if ($authstruct_raw !== null && strlen($authstruct_raw)) {
   try {
     $authstruct = phutil_json_decode($authstruct_raw);
   } catch (Exception $ex) {
@@ -135,7 +135,7 @@
 
   $cmd = csprintf('%s %Ls', $bin, $key_argv);
 
-  if (strlen($instance)) {
+  if ($instance !== null && strlen($instance)) {
     $cmd = csprintf('PHABRICATOR_INSTANCE=%s %C', $instance, $cmd);
   }
 
diff --git a/src/applications/almanac/util/AlmanacKeys.php b/src/applications/almanac/util/AlmanacKeys.php
--- a/src/applications/almanac/util/AlmanacKeys.php
+++ b/src/applications/almanac/util/AlmanacKeys.php
@@ -58,7 +58,7 @@
 
   public static function getClusterSSHUser() {
     $username = PhabricatorEnv::getEnvConfig('diffusion.ssh-user');
-    if (strlen($username)) {
+    if ($username !== null && strlen($username)) {
       return $username;
     }
 
diff --git a/src/applications/diffusion/controller/DiffusionRepositoryManagePanelsController.php b/src/applications/diffusion/controller/DiffusionRepositoryManagePanelsController.php
--- a/src/applications/diffusion/controller/DiffusionRepositoryManagePanelsController.php
+++ b/src/applications/diffusion/controller/DiffusionRepositoryManagePanelsController.php
@@ -40,7 +40,7 @@
     }
 
     $selected = $request->getURIData('panel');
-    if (!strlen($selected)) {
+    if ($selected === null || !strlen($selected)) {
       $selected = head_key($panels);
     }
 
diff --git a/src/applications/repository/editor/PhabricatorRepositoryEditor.php b/src/applications/repository/editor/PhabricatorRepositoryEditor.php
--- a/src/applications/repository/editor/PhabricatorRepositoryEditor.php
+++ b/src/applications/repository/editor/PhabricatorRepositoryEditor.php
@@ -50,7 +50,7 @@
     // If the repository does not have a local path yet, assign it one based
     // on its ID. We can't do this earlier because we won't have an ID yet.
     $local_path = $object->getLocalPath();
-    if (!strlen($local_path)) {
+    if ($local_path === null || !strlen($local_path)) {
       $local_key = 'repository.default-local-path';
 
       $local_root = PhabricatorEnv::getEnvConfig($local_key);
diff --git a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
--- a/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
+++ b/src/applications/repository/engine/PhabricatorRepositoryPullEngine.php
@@ -238,7 +238,7 @@
     $identifier = $repository->getPHID();
 
     $instance = PhabricatorEnv::getEnvConfig('cluster.instance');
-    if (strlen($instance)) {
+    if ($instance !== null && strlen($instance)) {
       $identifier = "{$identifier}:{$instance}";
     }
 
@@ -575,7 +575,7 @@
       $ref_rules);
 
     // Empty repositories don't have any refs.
-    if (!strlen(rtrim($stdout))) {
+    if ($stdout === null || !strlen(rtrim($stdout))) {
       return array();
     }
 
diff --git a/src/applications/repository/query/PhabricatorRepositoryRefCursorQuery.php b/src/applications/repository/query/PhabricatorRepositoryRefCursorQuery.php
--- a/src/applications/repository/query/PhabricatorRepositoryRefCursorQuery.php
+++ b/src/applications/repository/query/PhabricatorRepositoryRefCursorQuery.php
@@ -132,7 +132,7 @@
         $name_hashes);
     }
 
-    if (strlen($this->datasourceQuery)) {
+    if ($this->datasourceQuery !== null && strlen($this->datasourceQuery)) {
       $where[] = qsprintf(
         $conn,
         'refNameRaw LIKE %>',
diff --git a/src/applications/repository/storage/PhabricatorRepository.php b/src/applications/repository/storage/PhabricatorRepository.php
--- a/src/applications/repository/storage/PhabricatorRepository.php
+++ b/src/applications/repository/storage/PhabricatorRepository.php
@@ -345,7 +345,7 @@
 
     // Make some reasonable effort to produce reasonable default directory
     // names from repository names.
-    if (!strlen($name)) {
+    if ($name === null || !strlen($name)) {
       $name = $this->getName();
       $name = phutil_utf8_strtolower($name);
       $name = preg_replace('@[ -/:->]+@', '-', $name);
@@ -721,14 +721,14 @@
     $head = idx($params, 'head');
     $against = idx($params, 'against');
 
-    if ($req_commit && !strlen($commit)) {
+    if ($req_commit && ($commit === null || !strlen($commit))) {
       throw new Exception(
         pht(
           'Diffusion URI action "%s" requires commit!',
           $action));
     }
 
-    if ($req_branch && !strlen($branch)) {
+    if ($req_branch && ($branch === null || !strlen($branch))) {
       throw new Exception(
         pht(
           'Diffusion URI action "%s" requires branch!',
@@ -779,20 +779,20 @@
         break;
       case 'compare':
         $uri = $this->getPathURI("/{$action}/");
-        if (strlen($head)) {
+        if ($head !== null && strlen($head)) {
           $query['head'] = $head;
-        } else if (strlen($raw_commit)) {
+        } else if ($raw_commit !== null && strlen($raw_commit)) {
           $query['commit'] = $raw_commit;
-        } else if (strlen($raw_branch)) {
+        } else if ($raw_branch !== null && strlen($raw_branch)) {
           $query['head'] = $raw_branch;
         }
 
-        if (strlen($against)) {
+        if ($against !== null && strlen($against)) {
           $query['against'] = $against;
         }
         break;
       case 'branch':
-        if (strlen($path)) {
+        if ($path != null && strlen($path)) {
           $uri = $this->getPathURI("/repository/{$path}");
         } else {
           $uri = $this->getPathURI('/');
@@ -1160,7 +1160,7 @@
    */
   public function getRemoteURIObject() {
     $raw_uri = $this->getDetail('remote-uri');
-    if (!strlen($raw_uri)) {
+    if ($raw_uri === null || !strlen($raw_uri)) {
       return new PhutilURI('');
     }
 
@@ -2818,7 +2818,7 @@
     $permanent_rules = $this->getStringListForConduit($permanent_rules);
 
     $default_branch = $this->getDefaultBranch();
-    if (!strlen($default_branch)) {
+    if ($default_branch === null || !strlen($default_branch)) {
       $default_branch = null;
     }
 
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -2363,7 +2363,9 @@
         // Here, we don't care about processing only new mentions after an edit
         // because there is no way for an object to ever "unmention" itself on
         // another object, so we can ignore the old value.
-        $engine->markupText($change->getNewValue());
+        if ($change->getNewValue() !== null) {
+          $engine->markupText($change->getNewValue());
+        }
 
         $mentioned_phids += $engine->getTextMetadata(
           PhabricatorObjectRemarkupRule::KEY_MENTIONED_OBJECTS,
diff --git a/src/infrastructure/contentsource/PhabricatorUnknownContentSource.php b/src/infrastructure/contentsource/PhabricatorUnknownContentSource.php
--- a/src/infrastructure/contentsource/PhabricatorUnknownContentSource.php
+++ b/src/infrastructure/contentsource/PhabricatorUnknownContentSource.php
@@ -7,7 +7,7 @@
 
   public function getSourceName() {
     $source = $this->getSource();
-    if (strlen($source)) {
+    if ($source !== null && strlen($source)) {
       return pht('Unknown ("%s")', $source);
     } else {
       return pht('Unknown');
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
@@ -30,7 +30,7 @@
   public function renderPropertyViewValue(array $handles) {
     $value = $this->getFieldValue();
 
-    if (!strlen($value)) {
+    if ($value === null || !strlen($value)) {
       return null;
     }