TG: Sanity checks, miscellaneous bugfixes, failsafes.

Disposals no longer indiscriminately let items land inside it - the items have
to have been thrown by someone.

The ongoing attempt to fix the thousands of runtimes plaguing the game.
Revision: r3195
Author: 	 vageyenaman

code/modules/mob/living/carbon/human/human.dm

@@ -1860,8 +1860,9 @@ It can still be worn/put on as normal.
 				if (W)
 					W.loc = target.loc
 					W.dropped(target)
-					W.layer = initial(W.layer)
-				W.add_fingerprint(source)
+					if (W)
+						W.layer = initial(W.layer)
+						W.add_fingerprint(source)
 			else
 				if(!item) return
 				if (istype(item, /obj/item/clothing/mask))