Fixes #857, adds sanity check to dogborgs

Fixes #857

code/modules/mob/living/silicon/robot/dogborg/dog_sleeper_vr.dm

@@ -192,6 +192,9 @@
 		if(!cleaning)
 			var/confirm = alert(usr, "You are about to engage self-cleaning mode. This will fill your [src] with caustic enzymes to remove any objects or biomatter, and convert them into energy. Are you sure?", "Confirmation", "Self-Clean", "Cancel")
 			if(confirm == "Self-Clean")
+				if(cleaning)
+					return
+				else
 					cleaning = 1
 					drain(500)
 					processing_objects.Add(src)