Assistant crashes when remote controlled and gets syncContents

If the assistant is used in mode remoteControl and receives a syncContents command together or directly after setSource the assistant
crashes most times on startup. It seems the assistant tries to build the indexes in the compiled help after startup and receives the
syncContents command and this two "jobs" are not syncronized. This bug is maybe related to QTBUG-11342.
Before fixing this bug the syncContents did not work at all. Not it works sometimes .
Attached is a slightly modified QT example from help directory (remotecontrol).
Replace the original remotecontrol.cpp with the modified and recompile.
After that start the sample and press the button "Launch Qt Help Viewer".
Most times the assistant starts and then crashes. Sometimes it works. So if the assistant
does not crash immediately, try several times and you will see the crash of assistant.
To see the bug please close the assistant before trying again. If the assistant is up and running
the crash does not happen. It happens always after start of assistant!
Also a Stackdump of the assistant in case of the crash is attached.