Crash when canceling tasks

[d4rken]

java.lang.NullPointerException: Attempt to read from field 'eu.thedarken.sdm.tools.shell.a$d eu.thedarken.sdm.tools.shell.a.c' on a null object reference
        at eu.thedarken.sdm.tools.shell.InteractiveShell.doCallback(InteractiveShell.java:618)
        at eu.thedarken.sdm.tools.shell.InteractiveShell.exit(InteractiveShell.java:450)
        at eu.thedarken.sdm.tools.shell.ShellSource.cancel(ShellSource.java:107)
        at eu.thedarken.sdm.tools.shell.InteractiveShell.cancel(InteractiveShell:375)
        at eu.thedarken.sdm.tools.worker.AbstractWorker.onCleanup(AbstractWorker.java:199)
        at eu.thedarken.sdm.tools.worker.AbstractWorker.cleanup(AbstractWorker.java:207)
        at eu.thedarken.sdm.tools.worker.AbstractWorker.cancel(AbstractWorker.java:218)
        at eu.thedarken.sdm.ui.AbstractWorkerUIFragment.lambda$null$0(AbstractWorkerUIFragment.java:114)
        at eu.thedarken.sdm.ui.c.run(Unknown:-1)
        at java.lang.Thread.run(Thread.java:818)

[d4rken]

cancel(true) -> exit(true) cleared the current command without syncronization(this). This would race against the output streams onStreamClosed(). Which due to the race condition and missing syncronization found a left over command while processing weDead(). While processing the callback for this "orphaned" current command, the cancel() would clear the command reference, leading to an NPE.

[d4rken]

1506151829323 W/DatabasesWorker: Canceling...
1506151829323 W/AppCleanerWorker: Already canceled or not working!
1506151829323 D/DatabasesWorker: Cleaning up after task (force:true)
(...)
1506151841748 D/Shell:Interactive: Orphaned command, letting it know the bad news. Command(commands=[cd '/data/user/0/eu.thedarken.sdm/files', $V5B9D812A9C51 test -f '/storage/emulated/0/Android/data/com.tomtom.gplay.navapp/files/data/maps/16/Europe/extra.sqlite' && ./sqlite3_sdm '/storage/emulated/0/Android/data/com.tomtom.gplay.navapp/files/data/maps/16/Europe/extra.sqlite' VACUUM ])
1506151841748 D/Shell:Interactive: ...exiting completed! (globalExitcode=-4)
1506151841749 D/Shell:Interactive: runCommand(...): Command.Result(exitcode=-4)
1506151841749 W/Databases:DBTool: VACUUM failed for /storage/emulated/0/Android/data/com.tomtom.gplay.navapp/files/data/maps/16/Europe/extra.sqlite with []
1506151841749 W/Shell:Interactive: weDead(), but have an outstanding command: Command(commands=[cd '/data/user/0/eu.thedarken.sdm/files', $V5B9D812A9C51 test -f '/storage/emulated/0/Android/data/com.tomtom.gplay.navapp/files/data/maps/16/Europe/extra.sqlite' && ./sqlite3_sdm '/storage/emulated/0/Android/data/com.tomtom.gplay.navapp/files/data/maps/16/Europe/extra.sqlite' VACUUM ])
java.lang.NullPointerException: Attempt to read from field 'eu.thedarken.sdm.tools.shell.a$d eu.thedarken.sdm.tools.shell.a.c' on a null object reference
	at eu.thedarken.sdm.tools.shell.d.a(InteractiveShell.java)
	at eu.thedarken.sdm.tools.shell.d.b(InteractiveShell.java)
	at eu.thedarken.sdm.tools.shell.d$2.a(InteractiveShell.java)
	at eu.thedarken.sdm.tools.shell.b.run(Harvester.java)