Restore gravity/warp lines sticking out a tile offscreen

I just discovered this: whereas 2.3 and older versions make gravity
and warp lines - when placed in the editor - stick out one tile
offscreen, the latest version stops the lines at the room border.

This change restores the old behavior, and it's a simple fix: the
refactored code was written to let tiles outside the room block
gravity/warp lines. Instead of all offscreen tiles blocking lines, now
there's a 1-tile padding around the room that will let them through.

desktop_version/src/Editor.cpp

@@ -4039,6 +4039,11 @@ bool editorclass::lines_can_pass(int x, int y)
     {
         return tile == 0 || tile >= 680;
     }
+    if (x == -1 || y == -1 || x == SCREEN_WIDTH_TILES || y == SCREEN_HEIGHT_TILES)
+    {
+        // If lines go offscreen, they stick out one tile
+        return true;
+    }
     return false;
 }