[s] fix plasmapistol exploit (ParadiseSS13#27477)

code/modules/projectiles/guns/energy/special_eguns.dm

@@ -523,9 +523,17 @@
 	to_chat(user, "<span class='notice'>You begin to overload [src].</span>")
 	charging = TRUE
 	charge_failure = FALSE
+	holder = user
+	RegisterSignal(holder, COMSIG_CARBON_SWAP_HANDS, PROC_REF(fail_charge))
 	addtimer(CALLBACK(src, PROC_REF(overload)), 2.5 SECONDS)
 
+/obj/item/gun/energy/plasma_pistol/proc/fail_charge()
+	SIGNAL_HANDLER // COMSIG_CARBON_SWAP_HANDS
+	charge_failure = TRUE // No charging 2 guns at once.
+	UnregisterSignal(holder, COMSIG_CARBON_SWAP_HANDS)
+
 /obj/item/gun/energy/plasma_pistol/proc/overload()
+	UnregisterSignal(holder, COMSIG_CARBON_SWAP_HANDS)
 	if(ishuman(loc) && !charge_failure)
 		var/mob/living/carbon/C = loc
 		select_fire(C)