[NO GBP] Fixes catwalks over open space not making a sound when walked over. (#79738)

## About The Pull Request
See the title.

## Why It's Good For The Game
Actually fixing #78646.

## Changelog

🆑
fix: Fixed catwalks over open space not making a sound when walked over.
/🆑

code/__DEFINES/dcs/signals/signals_turf.dm

@@ -31,5 +31,7 @@
 
 ///from /datum/element/footstep/prepare_step(): (list/steps)
 #define COMSIG_TURF_PREPARE_STEP_SOUND "turf_prepare_step_sound"
+	//stops element/footstep/proc/prepare_step() from returning null if the turf itself has no sound
+	#define FOOTSTEP_OVERRIDEN (1<<0)
 ///from base of datum/thrownthing/finalize(): (turf/turf, atom/movable/thrownthing) when something is thrown and lands on us
 #define COMSIG_TURF_MOVABLE_THROW_LANDED "turf_movable_throw_landed"

code/datums/elements/footstep.dm

@@ -94,9 +94,9 @@
 		return
 
 	. = list(FOOTSTEP_MOB_SHOE = turf.footstep, FOOTSTEP_MOB_BAREFOOT = turf.barefootstep, FOOTSTEP_MOB_HEAVY = turf.heavyfootstep, FOOTSTEP_MOB_CLAW = turf.clawfootstep, STEP_SOUND_PRIORITY = STEP_SOUND_NO_PRIORITY)
-	SEND_SIGNAL(turf, COMSIG_TURF_PREPARE_STEP_SOUND, .)
+	var/overriden = SEND_SIGNAL(turf, COMSIG_TURF_PREPARE_STEP_SOUND, .) & FOOTSTEP_OVERRIDEN
 	//The turf has no footstep sound (e.g. open space) and none of the objects on that turf (e.g. catwalks) overrides it
-	if(isnull(turf.footstep))
+	if(!overriden && isnull(turf.footstep))
 		return null
 	return .
 

code/datums/elements/footstep_override.dm

@@ -78,3 +78,4 @@
 	steps[FOOTSTEP_MOB_HEAVY] = heavyfootstep
 	steps[FOOTSTEP_MOB_CLAW] = clawfootstep
 	steps[STEP_SOUND_PRIORITY] = priority
+	return FOOTSTEP_OVERRIDEN