Fixes Deep-Fried Grabs and Display Case Grabs (#7240)

* Fixes Grab's on Lethal Kitchen

Fixes the issue that I didn't have in testing. Fixes #7239

🆑 Twinmold
Fix: No longer able to cook grabs.
/🆑

* Fixes Display Case

Fixes #7212

* Changes Display Case to use ABSTRACT

So you can't put Ei'Nath into the case... Also, you already can't put
things like that in the deep fryer/other kitchen equipment, so that's
good.

code/game/objects/structures/displaycase.dm

@@ -256,6 +256,9 @@ var/global/list/captain_display_cases = list()
 			new /obj/machinery/constructable_frame/machine_frame(T)
 		qdel(src)
 		return
+	if(W.flags & ABSTRACT)
+		to_chat(user, "<span class='danger'>You can't put this into the case.</span>")
+		return
 	if(user.a_intent == I_HARM)
 		if(locked && !destroyed)
 			src.health -= W.force