This was a known issue already in 2009. Unfortunately, the person who had brought up the issue did not go further to actually file a bugreport. You can read the corresponding thread here:
http://marc.info/?l=webkit-dev&m=124888472218111&w=2
I would suggest to go ahead and create a bug report if it is still present with Qt 5.2.
Note that, in an ideal world, as written, you should not have a heap object for this operation, although it is slightly off-topic as it would not fix your issue. Yet, it is better to be aware of that a stack object here would do your job without the manual deletion headache.