[MIRROR] Cult pylons won't convert floorless floors (#692)

* Cult pylons won't convert floorless floors (#81171)

## About The Pull Request

Cult pylons read from our existing list of "turfs which don't count as
floor despite being open turfs" instead of having its own one, which did
not include openspace turfs.
This prevents it from "papering over" things like stairwells and sealing
people inside their base.


![image](https://github.com/tgstation/tgstation/assets/7483112/f91ad4a3-8546-4861-9098-31817ea30821)

## Why It's Good For The Game

It's not supposed to do that, and fixing it this way is futureproof to a
greater degree.

## Changelog

:cl:
fix: Cult pylons will no longer cover up "open space" (or water) with
cult floors
/:cl:

* Cult pylons won't convert floorless floors

---------

Co-authored-by: Jacquerel <[email protected]>

code/modules/antagonists/cult/cult_structure_pylon.dm

@@ -48,12 +48,9 @@
 		var/static/list/blacklisted_pylon_turfs = typecacheof(list(
 			/turf/closed,
 			/turf/open/floor/engine/cult,
-			/turf/open/space,
-			/turf/open/lava,
-			/turf/open/chasm,
 			/turf/open/misc/asteroid,
 		))
-		if(is_type_in_typecache(nearby_turf, blacklisted_pylon_turfs))
+		if(isgroundlessturf(nearby_turf) || is_type_in_typecache(nearby_turf, blacklisted_pylon_turfs))
 			continue
 		validturfs |= nearby_turf