question: public static boolean isNull ( final Object model , final String columnName ) { if ( model == null ) { return true ; } else if ( GridTabWrapper . isHandled ( model ) ) { return GridTabWrapper . isNull ( model , columnName ) ; } else if ( POWrapper . isHandled ( model ) ) { return POWrapper . isNull ( model , columnName ) ; } else { throw new AdempiereException ( "Model wrapping is not supported for " + model + " (class:" + model . getClass ( ) + ")" ) ; } }
target:  Check if given columnName's value is null