Small fix to VBL handler in room game

There's a flag that prevents most of the code in the VBL handler from
being executed twice at the same time. This patch makes the flag be
set right after testing if it is set or not. This isn't a real
problem right now because there's more than enough time to set the
flag after the test, but this way the code is easier to understand.

source/room_game/room_game.asm

@@ -1053,20 +1053,21 @@ RoomGameVBLHandler:
     ld      a,b
     ld      [game_sprites_8x16],a
 
-
+    ; Make sure that the following code isn't executed twice even if it doesn't
+    ; finish in one frame.
     ld      a,[vbl_handler_working]
     and     a,a
     ret     nz ; already working
 
+    ld      a,1
+    ld      [vbl_handler_working],a ; flag as working
+
     ld      a,[rSVBK]
     ld      b,a
     ld      a,[rVBK]
     ld      c,a
     push    bc
 
-    ld      a,1
-    ld      [vbl_handler_working],a ; flag as working
-
     ; Allow another VBL (or STAT) interrupt to happen and update graphics. Since
     ; vbl_handler_working is set to 1, they will only update graphics and return
     ; before handling user input.