If allow_show_all is disabled, we change the default category to the
first available category on the fly, if the chosen default category is
not contained in the available categories. We also make sure that we
do not show the "show all" category for the default category selection
in the category editor.
If
allow_show_allis disabled, we change the default category to the first available category on the fly, if the chosen default category is not contained in the available categories. We also make sure that we do not show the "show all" category for the default category selection in the category editor.