Comment 2 for bug 1913672

Incomplete because we don't have any line number info, any log messages telling us what the assertion is, or any test case.

We're left to guess, and my guess is either:

* An inlined function with an explicit assertion; or

* One of these macros:

  StBinPrivate *priv = st_bin_get_instance_private (ST_BIN (self));
  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));