Check executables exist in PATH before passing starting process
See: https://kde.org/info/security/advisory-20220131-1.txt https://mail.kde.org/pipermail/kde-devel/2022-January/000943.html
Add a unittest.
KListOpenFilesJob: check lsof executable exist in PATH before starting it with QProcess
KProcess: replace an assert with a check for empty
Calling QList::takeFirst() on an empty list would a crash.