Fixes #8700

code/modules/reagents/dispenser/dispenser2.dm

@@ -89,6 +89,10 @@
 			C.loc = loc
 
 	else if(istype(W, /obj/item/weapon/reagent_containers/glass) || istype(W, /obj/item/weapon/reagent_containers/food))
+		if(container)
+			user << "<span class='warning'>There is already \a [container] on \the [src]!</span>"
+			return
+
 		var/obj/item/weapon/reagent_containers/RC = W
 
 		if(!accept_drinking && istype(RC,/obj/item/weapon/reagent_containers/food))
@@ -172,4 +176,4 @@
 /obj/machinery/chemical_dispenser/attack_hand(mob/user as mob)
 	if(stat & BROKEN)
 		return
-	ui_interact(user)
+	ui_interact(user)