Removes putting machines in walls (#2237)

<!-- Write **BELOW** The Headers and **ABOVE** The comments else it may
not be viewable. -->
<!-- You can view Contributing.MD for a detailed description of the pull
request process. -->

## About The Pull Request
False walls will now only close if their tile is completely clear.
(unless it's atmospheric machinery or cables.
<!-- Describe The Pull Request. Please be sure every change is
documented or this can delay review and even discourage maintainers from
merging your PR! -->

## Why It's Good For The Game
Stops some troll logicing machinery into walls, making open space more
of a premium than it currently is
<!-- Please add a short description of why you think these changes would
benefit the game. If you can't justify it in words, it might not be
worth adding. -->

## Changelog

:cl:
tweak: you can no longer close falsewalls on tiles with machines or
structures on them
/:cl:

<!-- Both :cl:'s are required for the changelog to work! You can put
your name to the right of the first :cl: if you want to overwrite your
GitHub username as author ingame. -->
<!-- You can use multiple of the same prefix (they're only used for the
icon ingame) and delete the unneeded ones. Despite some of the tags,
changelogs should generally represent how a player might be affected by
the changes rather than a summary of the PR's contents. -->

---------

Co-authored-by: Mark Suckerberg <[email protected]>

code/game/objects/structures/false_walls.dm

@@ -40,8 +40,13 @@
 	opening = TRUE
 	update_appearance()
 	if(!density)
-		var/srcturf = get_turf(src)
-		for(var/mob/living/obstacle in srcturf) //Stop people from using this as a shield
+		var/turf/srcturf = get_turf(src)
+		if(locate(/mob/living) in srcturf) //Stop people from using this as a shield
+			opening = FALSE
+			return
+		for(var/atom/blocker as anything in srcturf)
+			if(!blocker.density) //Doesn't block
+				continue
 			opening = FALSE
 			return
 	addtimer(CALLBACK(src, /obj/structure/falsewall/proc/toggle_open), 5)