Deprecated functionality: preg_replace() (OpenMage#4311)

* Deprecated functionality: preg_replace()

* string casting

Replacement nulli-coalescing operator with string casting.

Author: addison74

app/code/core/Mage/Adminhtml/Block/System/Config/Form/Field.php

@@ -42,7 +42,7 @@ public function render(Varien_Data_Form_Element_Abstract $element)
         $isMultiple = $element->getExtType() === 'multiple';
 
         // replace [value] with [inherit]
-        $namePrefix = preg_replace('#\[value\](\[\])?$#', '', $element->getName());
+        $namePrefix = preg_replace('#\[value\](\[\])?$#', '', (string) $element->getName());
 
         $options = $element->getValues();