Only retrieve categories list if post type supports categories

[niallkennedy]

The get_the_category_list function attempts to pull a list of categories before it checks if a category relationship applies to the current post_type. Attached patch moves the category retrieval down a few lines: after we've determined a category relationship could exist.

Before

• Fetch and assign all categories to a variable
• Test if post type uses categories

After

• Test if post type uses categories
• Fetch and assign all categories to a variable

Saves fetch time and filtering for post types without a category relationship.

[niallkennedy]

attempt to fetch categories if categories applicable for post type

[nacin]

In [20622]:

Don't call get_the_category() in get_the_category_list() unless the post type supports categories. props niallkennedy. fixes #19671.