Workaround a crash on Mac OS X after finishing code review.

On OS X, kdevelop would crash after clicking on the "Finish Review"
button, at least when the path review tool was started through a
project's git->differences. This crash occurred with the current
stable release (kdevplatform 1.6.0) through the 4.7ß up to and
including kdevplatform git/kde4-legacy.

REVIEW: 120081
BUG: 338829