Call by reference deprecated at $form = erp_stock_edit_form(&$form_state, $nid);

The & character has to be removed from erp_stock_edit_form(&$form_state, $nid) function in erp_stock.module at line 748.
It is throwing this warning:
"Call-time pass-by-reference has been deprecated; If you would like to pass it by reference, modify the declaration of erp_stock_edit_form(). If you would like to enable call-time pass-by-reference..."