attached is my proposed patch for this bug.
It seems as far as I understand it that we trigger an bug in KRecentFiles.
We are opening an file via urlSelected and then add that url again.
And then sometimes it crashes (see the BTS with an backtrace).
My patch just moves the signal emitting to only by hand opened projects.
If this is a bit unconvenient (projects opened by commandline etc. are
ignored) we can also create a new function which handels this better.