Check msgSvc() is not null

This fixes a crash in athenaHLT jobs

fixes ATR-15094

See merge request !222

GaudiKernel/GaudiKernel/CommonMessaging.h

@@ -188,7 +188,9 @@ protected:
   /// This function is meant to be called by the update handler of the OutputLevel property.
   void updateMsgStreamOutputLevel(int level) {
     if (level != MSG::NIL && level != m_level) {
-      msgSvc()->setOutputLevel(this->name(), level);
+      if (msgSvc()) {
+        msgSvc()->setOutputLevel(this->name(), level);
+      }
       if (m_msgStream) m_msgStream->setLevel(level);
       if (UNLIKELY(MSG::Level(level) <= MSG::DEBUG))
         debug() << "Property update for OutputLevel : new value = " << level << endmsg;