Update to address another clear related issue

src/PHPHtmlParser/Dom/AbstractNode.php

@@ -169,8 +169,8 @@ public function delete()
         if ( ! is_null($this->parent)) {
             $this->parent->removeChild($this->id);
         }
-
-        $this->parent = null;
+        $this->parent->clear();
+        $this->clear();
     }
 
     /**
@@ -307,7 +307,7 @@ public function setAttribute($key, $value)
 
         //clear any cache
         $this->clear();
-        
+
         return $this;
     }
 
@@ -321,7 +321,7 @@ public function setAttribute($key, $value)
     public function removeAttribute($key)
     {
         $this->tag->removeAttribute($key);
-        
+
         //clear any cache
         $this->clear();
     }
@@ -335,7 +335,7 @@ public function removeAttribute($key)
     public function removeAllAttributes()
     {
         $this->tag->removeAllAttributes();
-        
+
         //clear any cache
         $this->clear();
     }

src/PHPHtmlParser/Dom/HtmlNode.php

@@ -186,6 +186,9 @@ protected function clear()
         $this->innerHtml = null;
         $this->outerHtml = null;
         $this->text      = null;
+        if (is_null($this->parent) === false) {
+            $this->parent->clear();
+        }
     }
 
     /**

src/PHPHtmlParser/Dom/MockNode.php

@@ -40,6 +40,9 @@ protected function clear()
         $this->innerHtml = null;
         $this->outerHtml = null;
         $this->text      = null;
+        if (is_null($this->parent) === false) {
+            $this->parent->clear();
+        }
     }
 
     /**