Posts, Post Types: Avoid a PHP warning when get_the_content() is called outside of the loop.

This ensures that `$pages` and other globals are only used after they have been set up in `setup_postdata()`.

Follow-up to [44941].

Props tessawatkinsllc, dontdream, spacedmonkey, squarecandy, davidbaumwald, SergeyBiryukov.
Fixes #47824. See #42814.

git-svn-id: https://develop.svn.wordpress.org/trunk@48114 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-query.php

@@ -4275,7 +4275,7 @@ class WP_Query {
 		$numpages     = $elements['numpages'];
 
 		/**
-		 * Fires once the post data has been setup.
+		 * Fires once the post data has been set up.
 		 *
 		 * @since 2.8.0
 		 * @since 4.1.0 Introduced `$this` parameter.