Fix null pointer runtime in scheduled task controller.

* If the "scheduler" controller is restarted by the process scheduler for
any reason, it will start throwing runtimes every status panel update
because the new replacement instance doesn't initialize its list of
schedule tasks.
* Fix that by copying over the unfinished list from the old instance, but
doing some safety checks to make sure it doesn't copy over bad stuff.

code/controllers/Processes/scheduler.dm

@@ -25,6 +25,21 @@
 			catchException(e, last_object)
 		SCHECK
 
+// We've been restarted, probably due to having a massive list of tasks.
+// Lets copy over the task list as safely as we can and try to chug thru it...
+// Note: We won't be informed about tasks being destroyed, but this is the best we can do.
+/datum/controller/process/scheduler/copyStateFrom(var/datum/controller/process/scheduler/target)
+	scheduled_tasks = list()
+	for(var/st in target.scheduled_tasks)
+		if(!deleted(st) && istype(st, /datum/scheduled_task))
+			schedule(st)
+	scheduler = src
+
+// We are being killed. Least we can do is deregister all those events we registered
+/datum/controller/process/scheduler/onKill()
+	for(var/st in scheduled_tasks)
+		destroyed_event.unregister(st, src)
+
 /datum/controller/process/scheduler/statProcess()
 	..()
 	stat(null, "[scheduled_tasks.len] task\s")