postpone jump out on AJAX calls for Statify 1.7 compatibility (#22)

Statify 1.7 changed the JS tacking endpoint to WP AJAX, so we must not
skip the complete initialization on AJAX calls anymore. The routine now
breaks after adding the filter (if necessary).

README.md

@@ -90,6 +90,9 @@ Same for IPv6 prefixes like _2001:db8:a0b:12f0::/64_.
 
 ## Changelog ##
 
+### 1.5.1 / unreleased ###
+* Fix initialization on AJAX calls for _Statify_ 1.7 compatibility
+
 ### 1.5.0 / 13.05.2020 ###
 * Minimum required WordPress version is 4.7
 * Removed `load_plugin_textdomain()` and `Domain Path` header

inc/class-statifyblacklist.php

@@ -81,8 +81,8 @@ class StatifyBlacklist {
 	 * @return void
 	 */
 	public static function init() {
-		// Skip on autosave or AJAX.
-		if ( ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) || ( defined( 'DOING_AJAX' ) && DOING_AJAX ) ) {
+		// Skip on autosave.
+		if ( ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) ) {
 			return;
 		}
 
@@ -97,6 +97,11 @@ public static function init() {
 			add_filter( 'statify__skip_tracking', array( 'StatifyBlacklist', 'apply_blacklist_filter' ) );
 		}
 
+		// Statify uses WP AJAX as of 1.7, so we need to reach this point. But there are no further admin/cron actions.
+		if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
+			return;
+		}
+
 		// Admin only filters.
 		if ( is_admin() ) {
 			StatifyBlacklist_Admin::init();