When a user Execute-Launches an application a second time while the
previously launched instance of this application is still running, the
"Job Already Running" dialog appears with 3 buttons. If a user clicks
the Cancel button, a NativeAppJob kills itself Quietly. This
NativeAppJob belongs to an ExecuteCompositeJob, which is not notified
when a subjob is killed Quietly. So the ExecuteCompositeJob keeps
waiting for it to finish. When this waiting ExecuteCompositeJob is
killed (e.g. via "Stop All" button or on KDevelop exit), it attempts to
kill the subjob it believes is still running, but which in fact is long
since destroyed. This usually causes a segmentation fault.

Aleix Pol fixed a similar crash when the "Kill All Instances" button in
the "Job Already Running" dialog is clicked in
8430d305.

BUG: 399511, 416874
FIXED-IN: 5.6.1