Fixes robot limbs spamming sparks and messages endlessly

Fixes robot limbs spamming malfunctioning messages and spark effects
endlessly if one arm is malfunctioning while holding an item in the
other arm.

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

@@ -118,8 +118,12 @@
 		else if(E.is_malfunctioning())
 
 			if(E.body_part == HAND_LEFT)
+				if(!l_hand)
+					continue
 				drop_from_inventory(l_hand)
 			else
+				if(!r_hand)
+					continue
 				drop_from_inventory(r_hand)
 
 			emote("me", 1, "drops what they were holding, their [E.name] malfunctioning!")