message: gtk: check NULL before unref
diff: @@ -951,6 +951,7 @@ static gboolean cvImageWidget_draw(GtkWidget* widget, cairo_t *cr, gpointer data
  }
  cairo_paint(cr);
  + if(pixbuf)
  g_object_unref(pixbuf);
  return TRUE;
  }
  @@ -1005,6 +1006,7 @@ static gboolean cvImageWidget_expose(GtkWidget* widget, GdkEventExpose* event, g
  }
  cairo_paint(cr);
  + if(pixbuf)
  g_object_unref(pixbuf);
  cairo_destroy(cr);
  return TRUE;
  