question: private String checkTrainId ( ) { String msg = null ; if ( _warrant . getRunMode ( ) != Warrant . MODE_NONE ) { msg = _warrant . getRunModeMessage ( ) ; return msg ; } List < BlockOrder > orders = getOrders ( ) ; if ( orders . size ( ) == 0 ) { msg = Bundle . getMessage ( "NoRouteSet" , _origin . getBlockName ( ) , _destination . getBlockName ( ) ) ; return msg ; } msg = _warrant . setRoute ( 0 , orders ) ; if ( msg != null ) { return msg ; } msg = checkLocoAddress ( ) ; return msg ; }
target:  all non-null returns are fatal