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

tests/phpunit/tests/post/getTheContent.php

@@ -75,4 +75,13 @@ class Tests_Post_GetTheContent extends WP_UnitTestCase {
 
 		$this->assertSame( 'Bang', $found );
 	}
+
+	/**
+	 * @ticket 47824
+	 */
+	public function test_should_fall_back_to_post_global_outside_of_the_loop() {
+		$GLOBALS['post'] = self::factory()->post->create( array( 'post_content' => 'Foo' ) );
+
+		$this->assertSame( 'Foo', get_the_content() );
+	}
 }