spudec: set the subpicture original dimensions based on the SPU prope…

…rties

If p_spu_properties->i_x/y is set (a few lines below), then the width/height
too.

modules/codec/spudec/parse.c

@@ -871,6 +871,13 @@ static int Render( decoder_t *p_dec, subpicture_t *p_spu,
     }
     vlc_spu_regions_push(&p_spu->regions, p_region);
 
+    if (p_spu->i_original_picture_width == 0 && p_spu->i_original_picture_height == 0)
+    {
+        assert(p_spu_properties->i_width != 0);
+        assert(p_spu_properties->i_height != 0);
+        p_spu->i_original_picture_width  = p_spu_properties->i_width;
+        p_spu->i_original_picture_height = p_spu_properties->i_height;
+    }
     p_region->b_absolute = true;
     p_region->i_x = p_spu_properties->i_x;
     p_region->i_y = p_spu_properties->i_y + p_spu_data->i_y_top_offset;