Sometimes (~50%) searches fail in my install, and I'm shown this message: Unhandled Exception: Invalid UTF-8 string passed to phutil_utf8v()

Our install is still running mysql 5.4.

Per @epriestley in IRC earlier today:

epriestley: if you want to file an issue to remind me, I can probably fix it -- even on 5.4 I think it "shouldn't" be possible, but maybe less-impossible than I think.
epriestley: We don't have a "convert all the data everywhere to valid utf8" command and probably can't reasonbly build one other than storage/adjust + MySQL 5.5, but I think this particular case is a reasonable one to just work around -- we're only making that call to do highlighting of a search match.