(svn r3421) - Revert r3412 as it didn't work.

- Fix station builder issue by checking the tile is in bounds.

openttd.c

@@ -814,10 +814,6 @@ void SwitchMode(int new_mode)
 
 	if (_switch_mode_errorstr != INVALID_STRING_ID)
 		ShowErrorMessage(INVALID_STRING_ID,_switch_mode_errorstr,0,0);
-
-	// Reset the TileHighlightData as it may be out of bounds if
-	// the new map is smaller than the old map.
-	memset(&_thd, 0, sizeof(_thd));
 }