BUG: Incorrect excerpt when Excerpt highlighting is enabled

[burhandodhy]

Describe the bug

When the Excerpt highlighting is enabled, we call the get_the_excerpt function outside of the loop for the different post. It returns the excerpt of the post of main loop. This happened because get_the_content is looking for the content of main loop post.

Steps to Reproduce

1. Enable Excerpt highlighting option
2. Create a post and leave the excerpt empty
3. Search for that post through the code.

	$posts = get_posts( [ 's' => 'searchTerm' ] );
	var_dump( get_the_excerpt( $post[0] ) );

4. Returns the excerpt of different post.

Expected behavior

Should return the excerpt of correct post.

Additional context