From 7ef01161ed17eda65013d4acacb36aba5c9cf1ba Mon Sep 17 00:00:00 2001
From: Watermelon914 <37270891+Watermelon914@users.noreply.github.com>
Date: Sat, 9 Oct 2021 08:58:27 +0100
Subject: [PATCH] Fixed circuit variables not working because of a null
 listener in their listener list (#61961)

Co-authored-by: Watermelon914 <3052169-Watermelon914@users.noreply.gitlab.com>
---
 code/modules/wiremod/core/variable.dm | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/code/modules/wiremod/core/variable.dm b/code/modules/wiremod/core/variable.dm
index 2153688d7bf..2bebc4e7e89 100644
--- a/code/modules/wiremod/core/variable.dm
+++ b/code/modules/wiremod/core/variable.dm
@@ -38,10 +38,16 @@
 	for(var/obj/item/circuit_component/component as anything in listeners)
 		component.trigger_component()
 
+/datum/circuit_variable/proc/on_listener_qdel(datum/listener)
+	SIGNAL_HANDLER
+	listeners -= listener
+
 /// Adds a listener to receive inputs when the variable has a value that is set.
 /datum/circuit_variable/proc/add_listener(obj/item/circuit_component/to_add)
 	listeners += to_add
+	RegisterSignal(to_add, COMSIG_PARENT_QDELETING, .proc/on_listener_qdel)
 
 /// Removes a listener to receive inputs when the variable has a value that is set. Listener will usually clean themselves up
 /datum/circuit_variable/proc/remove_listener(obj/item/circuit_component/to_remove)
+	UnregisterSignal(to_remove, COMSIG_PARENT_QDELETING)
 	listeners -= to_remove