Repro steps:
- Create diff 1, which affects only file A.
- Update revision with diff 2, which affects only files other than A.
- Show diff of diffs between diffs 2 and 1.
- Leave a comment on the left hand side of file A.
- Save draft.
Actual result:
```
Invalid changeset ID!
Depth Library File Where
5 phabricator infrastructure/diff/PhabricatorInlineCommentController.php : 187 DifferentialInlineCommentEditController::createComment()
4 phabricator aphront/AphrontController.php : 33 PhabricatorInlineCommentController::processRequest()
3 phabricator aphront/configuration/AphrontApplicationConfiguration.php : 226 AphrontController::handleRequest()
2 phabricator aphront/configuration/AphrontApplicationConfiguration.php : 140 AphrontApplicationConfiguration::processRequest()
1 /Users/epriestley/dev/core/lib/phabricator/webroot/index.php : 19 AphrontApplicationConfiguration::runHTTPRequest()
```
Expected result:
- not that