Fix typo.

modules/video_filter/wall.c

@@ -428,7 +428,7 @@ static int Mouse( video_splitter_t *p_splitter, vlc_mouse_t *p_mouse,
     {
         for( int x = 0; x < p_sys->i_col; x++ )
         {
-            wall_output_t *p_output = p_output = &p_sys->pp_output[x][y];
+            wall_output_t *p_output = &p_sys->pp_output[x][y];
             if( p_output->b_active && p_output->i_output == i_index )
             {
                 *p_mouse = *p_new;