[MIRROR] Revert "Makes immerse use weakrefs", prioritizing some ref removal lines instead. [MDB IGNORE] (#26149)

* Revert "Makes immerse use weakrefs", prioritizing some ref removal lines instead. (#80707)

## About The Pull Request
For a moment, I had forgot about saying I'd take a look into it, but it
seems the new fix to hard dels is causing some runtimes with empty
weakrefs. Beside, WEAKREF() doesn't work well with qdeleting atoms (so
you'd have to access the weak_reference var directly).
How immersion works is quite confusing even for me who coded it, trying
to work around some of the hefty limitations of the engine truly blows.
I could even ask MrMelbert to make a proc-chain chart for it.

But yeah, long story short, I only have a bare idea where the uncleared
refs would be. I suspect it could be `immersed_movables`. It's totally
possible since the proc can early return in a few cases, thus skipping
the ref removal, hence the title.

## Why It's Good For The Game
I didn't like the PR that implemented weakref usage into the element,
but I let it pass because "hard dels = bad". However, the runtimes
aren't that much more pleasant either.

## Changelog
N/A

* Revert "Makes immerse use weakrefs", prioritizing some ref removal lines instead.

---------

Co-authored-by: Ghom <42542238+Ghommie@users.noreply.github.com>

code/datums/elements/immerse.dm

@@ -32,7 +32,7 @@
 	if(!isturf(target) || !icon || !icon_state || !mask_icon)
 		return ELEMENT_INCOMPATIBLE
 
-	if(!movables_to_ignore)
+	if(isnull(movables_to_ignore))
 		movables_to_ignore = typecacheof(list(
 			/obj/effect,
 			/mob/dead,
@@ -96,8 +96,8 @@
 /datum/element/immerse/proc/stop_immersion(turf/source)
 	SIGNAL_HANDLER
 	UnregisterSignal(source, list(COMSIG_ATOM_ABSTRACT_ENTERED, COMSIG_ATOM_AFTER_SUCCESSFUL_INITIALIZED_ON, COMSIG_ATOM_ABSTRACT_EXITED))
-	for(var/datum/weakref/movable as anything in attached_turfs_and_movables[source])
-		remove_from_element(source, movable.resolve())
+	for(var/atom/movable/movable as anything in attached_turfs_and_movables[source])
+		remove_from_element(source, movable)
 	attached_turfs_and_movables -= source
 
 /**
@@ -122,7 +122,7 @@
 
 	try_immerse(movable, buckled)
 	RegisterSignal(movable, COMSIG_QDELETING, PROC_REF(on_movable_qdel))
-	LAZYADD(attached_turfs_and_movables[source], WEAKREF(movable))
+	LAZYADD(attached_turfs_and_movables[source], movable)
 	ADD_TRAIT(movable, TRAIT_IMMERSED, ELEMENT_TRAIT(src))
 
 /datum/element/immerse/proc/on_movable_qdel(atom/movable/source)
@@ -170,7 +170,7 @@
 
 	movable.vis_contents |= vis_overlay
 
-	LAZYSET(immersed_movables, WEAKREF(movable), vis_overlay)
+	LAZYSET(immersed_movables, movable, vis_overlay)
 
 ///Initializes and caches a new visual overlay given parameters such as width, height and whether it should appear fully underwater.
 /datum/element/immerse/proc/generate_vis_overlay(width, height, is_below_water)
@@ -212,16 +212,14 @@
 
 ///This proc removes the vis_overlay, the keep together trait and some signals from the movable.
 /datum/element/immerse/proc/remove_immerse_overlay(atom/movable/movable)
-	var/atom/movable/immerse_overlay/vis_overlay = LAZYACCESS(immersed_movables, WEAKREF(movable))
-	if(!vis_overlay)
-		return
-	movable.vis_contents -= vis_overlay
-	LAZYREMOVE(immersed_movables, WEAKREF(movable))
-	if(HAS_TRAIT(movable, TRAIT_UNIQUE_IMMERSE))
-		UnregisterSignal(movable, list(COMSIG_ATOM_SPIN_ANIMATION, COMSIG_LIVING_POST_UPDATE_TRANSFORM))
-		qdel(vis_overlay)
+	var/atom/movable/immerse_overlay/vis_overlay = LAZYACCESS(immersed_movables, movable)
+	LAZYREMOVE(immersed_movables, movable)
 	REMOVE_KEEP_TOGETHER(movable, ELEMENT_TRAIT(src))
-
+	movable.vis_contents -= vis_overlay
+	if(HAS_TRAIT(movable, TRAIT_UNIQUE_IMMERSE))
+		UnregisterSignal(movable, list(COMSIG_ATOM_SPIN_ANIMATION, COMSIG_LIVING_POST_UPDATE_TRANSFORM, COMSIG_QDELETING))
+		if(!QDELETED(vis_overlay))
+			qdel(vis_overlay)
 /**
  * Called by init_or_entered() and on_set_buckled().
  * This applies the overlay if neither the movable or whatever is buckled to (exclusive to living mobs) are flying
@@ -298,8 +296,8 @@
 	if(!(exited.loc in attached_turfs_and_movables))
 		remove_from_element(source, exited)
 	else
-		LAZYREMOVE(attached_turfs_and_movables[source], WEAKREF(exited))
-		LAZYADD(attached_turfs_and_movables[exited.loc], WEAKREF(exited))
+		LAZYREMOVE(attached_turfs_and_movables[source], exited)
+		LAZYADD(attached_turfs_and_movables[exited.loc], exited)
 
 ///Remove any signal, overlay, trait given to the movable and reference to it within the element.
 /datum/element/immerse/proc/remove_from_element(turf/source, atom/movable/movable)
@@ -309,9 +307,9 @@
 		buckled = living_mob.buckled
 	try_unimmerse(movable, buckled)
 
+	LAZYREMOVE(attached_turfs_and_movables[source], movable)
 	UnregisterSignal(movable, list(COMSIG_LIVING_SET_BUCKLED, COMSIG_QDELETING))
 	REMOVE_TRAIT(movable, TRAIT_IMMERSED, ELEMENT_TRAIT(src))
-	LAZYREMOVE(attached_turfs_and_movables[source], WEAKREF(movable))
 
 /// A band-aid to keep the (unique) visual overlay from scaling and rotating along with its owner. I'm sorry.
 /datum/element/immerse/proc/on_update_transform(mob/living/source, resize, new_lying_angle, is_opposite_angle)
@@ -320,7 +318,7 @@
 	new_transform.Scale(1/source.current_size)
 	new_transform.Turn(-new_lying_angle)
 
-	var/atom/movable/immerse_overlay/vis_overlay = immersed_movables[WEAKREF(source)]
+	var/atom/movable/immerse_overlay/vis_overlay = immersed_movables[source]
 	if(is_opposite_angle)
 		vis_overlay.transform = new_transform
 		vis_overlay.adjust_living_overlay_offset(source)
@@ -361,7 +359,7 @@
 ///Spin the overlay in the opposite direction so it doesn't look like it's spinning at all.
 /datum/element/immerse/proc/on_spin_animation(atom/source, speed, loops, segments, segment)
 	SIGNAL_HANDLER
-	var/atom/movable/immerse_overlay/vis_overlay = immersed_movables[WEAKREF(source)]
+	var/atom/movable/immerse_overlay/vis_overlay = immersed_movables[source]
 	vis_overlay.do_spin_animation(speed, loops, segments, -segment)
 
 ///We need to make sure to remove hard refs from the element when deleted.