Fix #174 by cloning input DOMDocument instance

Author: Zegnat

Mf2/Parser.php

@@ -345,7 +345,7 @@ public function __construct($input, $url = null, $jsonMode = false) {
 				@$doc->loadHTML(unicodeToHtmlEntities($input));
 			}
 		} elseif (is_a($input, 'DOMDocument')) {
-			$doc = $input;
+			$doc = clone $input;
 		} else {
 			$doc = new DOMDocument();
 			@$doc->loadHTML('');