Fixes headrevs being able to be mindshielded (#21714)

* VIVAAAAA

* sirryan review

code/game/objects/items/weapons/implants/implant.dm

@@ -160,7 +160,9 @@
  *  -1 if the implant fails to inject
  * 	0 if there's no room for the implant.
  */
-/obj/item/implant/proc/implant(mob/source, mob/user)
+/obj/item/implant/proc/implant(mob/source, mob/user, force)
+	if(!force && !can_implant(source, user))
+		return
 	var/obj/item/implant/imp_e = locate(type) in source
 	if(!allow_multiple && imp_e && imp_e != src)
 		if(imp_e.uses < initial(imp_e.uses)*2)
@@ -200,6 +202,19 @@
 
 	return 1
 
+/**
+ * Check that we can actually implant this before implanting it
+ * * source - The person being implanted
+ * * user - The person doing the implanting
+ *
+ * Returns
+ * TRUE - I could care less, implant it, maybe don't. I don't care.
+ * FALSE - Don't implant!
+ */
+/obj/item/implant/proc/can_implant(mob/source, mob/user)
+	return TRUE
+
+
 /**
  * Clean up when an implant is removed.
  * * source - the user who the implant was removed from.

code/game/objects/items/weapons/implants/implant_mindshield.dm

@@ -6,6 +6,13 @@
 	implant_data = /datum/implant_fluff/mindshield
 	implant_state = "implant-nanotrasen"
 
+/obj/item/implant/mindshield/can_implant(mob/source, mob/user)
+	if(source.mind in SSticker.mode.head_revolutionaries)
+		source.visible_message("<span class='biggerdanger'>[source] seems to resist [src]!</span>",
+								"<span class='warning'>You feel something interfering with your mental conditioning, but you resist it!</span>")
+		return FALSE
+	return ..()
+
 /obj/item/implant/mindshield/implant(mob/target)
 	if(!..())
 		return FALSE