Prevent finishing initialization if not on frontend

Author: westonruter

includes/class-amp-theme-support.php

@@ -153,7 +153,9 @@ public static function init() {
 		 * the response at this action and then short-circuit with exit. So this is why the the preceding
 		 * action to template_redirect--the wp action--is used instead.
 		 */
-		add_action( 'wp', array( __CLASS__, 'finish_init' ), PHP_INT_MAX );
+		if ( ! is_admin() ) {
+			add_action( 'wp', array( __CLASS__, 'finish_init' ), PHP_INT_MAX );
+		}
 	}
 
 	/**