Added initialization of $op_Params to avoid warning on xml returned in webservice to disable a user.

main/inc/lib/nusoap/class.soap_server.php

@@ -661,6 +661,7 @@ class nusoap_server extends nusoap_base {
 			$this->debug('got a(n) '.gettype($this->methodreturn).' from method');
 			$this->debug('serializing return value');
 			if($this->wsdl){
+				$opParams = "";
 				if (sizeof($this->opData['output']['parts']) > 1) {
 					$this->debug('more than one output part, so use the method return unchanged');
 			    	$opParams = $this->methodreturn;