room: fix invalid walkable detection (#1453)

This avoids testing the floor height for the on walkable check when the
corresponding sector does not have a trigger. This is equivalent to
not finding a walkable object.

Resolves #1452.

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## [Unreleased](https://github.com/LostArtefacts/TR1X/compare/stable...develop) - ××××-××-××
 - fixed holstering pistols hiding the gun meshes 1 frame too early (#1449, regression from 0.6)
+- fixed Lara's sliding animation sometimes being interrupted by a stumble (#1452, regression from 4.3)
 - improved logs module names readability
 - improved crash debug information on Windows
 

src/game/room.c

@@ -1014,12 +1014,11 @@ bool Room_IsOnWalkable(
     const int32_t z, const int32_t room_height)
 {
     sector = Room_GetPitSector(sector, x, z);
-
-    int16_t height = sector->floor.height;
     if (sector->trigger == NULL) {
-        return room_height == height;
+        return false;
     }
 
+    int16_t height = sector->floor.height;
     bool object_found = false;
     for (int32_t i = 0; i < sector->trigger->command_count; i++) {
         const TRIGGER_CMD *const cmd = &sector->trigger->commands[i];