patch for three undefined variable or null warnings

Dear Rafael,

I would like to commit a little patch for three undefined variable or null warnings:

in superior-faq.php

@@ -268,7 +268,7 @@ if(!class_exists('Superior_FAQ')) {
 
                        global $post;
 
-                       if($post->post_type == 'faq') {
+                       if(isset($post->post_type) && $post->post_type == 'faq') {
                                //get selected template for faqs posts
                                $settings = get_option( 'superior_faq_settings' );
 
@@ -292,8 +292,9 @@ if(!class_exists('Superior_FAQ')) {
 
                        global $post;
 
-                   if ( is_admin() || $post->post_type != 'faq' ) return;
+                   if ( is_admin() || (isset($post->post_type) && $post->post_type != 'faq') ) return;
                    if ( empty ( $post_id) ) {
+                       if (! isset($post->ID) ) return;
                        $post_id = $post->ID;
                    }
 
@@ -315,7 +316,7 @@ if(!class_exists('Superior_FAQ')) {
                public function faq_content_filter( $content ) {
 
                        global $post;
-                       if($post->post_type == 'faq') {
+                       if(! is_null($post) && $post->post_type == 'faq') {
 
                                $settings = get_option( 'superior_faq_settings' );