plug-ins are missing for disabled base themes of enabled sub-themes

If a enabled sub-theme has a base theme that is disabled, all of the code from the disabled base theme is loaded for use by the sub-theme.

But unfortunately, plug-ins defined in a disabled base theme are not being loaded.

In the upcoming Drupal 6.15, the data returned by list_themes will include a "base_themes" array that has the list of base themes for each theme. That data would be mighty handy to use when fixing this bug. So, personally, I would be fine with the Panels bugfix only working wtih Drupal 6.15 and later.