message: sv2017: fix empty concatenation
diff: @@ -1418,7 +1418,7 @@ expression:
  ) ( attribute_instance )* expression #expressionArrows
  ;
  concatenation:
  - LBRACE expression ( concatenation | ( COMMA expression )+)? RBRACE;
  + LBRACE (expression ( concatenation | ( COMMA expression )+)?)? RBRACE;
  dynamic_array_new:
  KW_NEW LSQUARE_BR expression RSQUARE_BR ( LPAREN expression RPAREN )?;
  