Allow " and ' chars in orderBy

MysqliDb.php

@@ -713,7 +713,7 @@ class MysqliDb
     {
         $allowedDirection = Array ("ASC", "DESC");
         $orderbyDirection = strtoupper (trim ($orderbyDirection));
-        $orderByField = preg_replace ("/[^-a-z0-9\.\(\),_`\*]+/i",'', $orderByField);
+        $orderByField = preg_replace ("/[^-a-z0-9\.\(\),_`\*\'\"]+/i",'', $orderByField);
 
         // Add table prefix to orderByField if needed.
         //FIXME: We are adding prefix only if table is enclosed into `` to distinguish aliases
@@ -1239,8 +1239,10 @@ class MysqliDb
     {
         if ($this->isSubQuery)
             return;
-        if ($this->_mysqli)
+        if ($this->_mysqli) {
             $this->_mysqli->close();
+            $this->_mysqli = null;
+        }
     }
 
     /**