kio_filenamesearch: fix crash due to KCoreDirLister changes
Error reporting was changed in KCoreDirlister, to match the original behaviour we need to explicitly disable auto error handling.
This fixes a crash while searching in Dolphin, kio_filenamesearch intrenally uses a dirlister, and a nested event loop, if there is an error while listing some dir it tries to report it using a job ui delegate, but the parent job could well be dead by that time, which causes a crash: "QWidget: Cannot create a QWidget without QApplication"
Note that this crash only happens if KDE_FORK_SLAVES is not set.