tr2/room: fix floor height alteration creating walls

This fixes altering the floor height to a wall in the case where
pushblocks have been stacked and the one on top is touching the
ceiling.

docs/tr2/CHANGELOG.md

@@ -6,6 +6,8 @@
 - fixed Lara getting stuck in a T-pose after jumping/falling and then dying before reaching fast fall speed (#2575)
 - fixed a rare issue whereby Lara would be unable to move after disposing a flare (#2545, regression from 0.9)
 - fixed flare pickups only adding one flare to Lara's inventory rather than six (#2551, regression from 0.9)
+- fixed several issues with pushblocks (#2036)
+    - fixed an invisible wall above stacked pushblocks if near a ceiling portal
 - fixed play any level causing the game to hang when no gym level is present (#2560, regression from 0.9)
 - fixed extremely large item quantities crashing the game (#2497, regression from 0.3)
 - fixed missing new game text in the passport when play any level is enabled (#2563, regression from 0.9)

docs/tr2/README.md

@@ -80,6 +80,8 @@ game with new enhancements and features.
 - fixed the game crashing if a cinematic is triggered but the level contains no cinematic frames
 - fixed smashed windows blocking enemy pathing after loading a save
 - fixed Lara getting stuck in a T-pose after jumping/falling and then dying before reaching fast fall speed
+- fixed several issues with pushblocks
+    - fixed an invisible wall above stacked pushblocks if near a ceiling portal
 - improved the animation of Lara's braid
 
 #### Cheats

src/tr2/game/room.c

@@ -569,7 +569,8 @@ void Room_AlterFloorHeight(const ITEM *const item, const int32_t height)
         sector->floor.height = ceiling->ceiling.height + ROUND_TO_CLICK(height);
     } else {
         sector->floor.height += ROUND_TO_CLICK(height);
-        if (sector->floor.height == ceiling->ceiling.height) {
+        if (sector->floor.height == ceiling->ceiling.height
+            && sector->portal_room.sky == NO_ROOM) {
             sector->floor.height = NO_HEIGHT;
         }
     }