Observed on OSX 10.9.4 / LO 126.96.36.199 and master
Steps to reproduce:
1. Create a new Writer document containing "啊"
2. Select all
3. Open Tools - Language - Chinese Conversion... (requires Asian language support to be enabled in Options - Language Settings - Languages)
4. Click on "OK" ("Conversion Direction" can be either way)
However, this only occurs on my own build and not the release build of 188.8.131.52. This could be a result of differences in the build environment (release builds are still built on 10.6 ...) or the fact that assertions are not enabled for release
Created attachment 105371 [details]
4.4 master backtrace
I will take a stab at fixing this myself
Crashes on Linux, too.
Matthew J. Francis committed a patch related to this issue.
It has been pushed to "master":
fdo#83178 fix Chinese Conversion crash
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.