message: Fix codegen for Optional Catch Binding
  Closes
diff: @@ -12,10 +12,12 @@ export default function CatchClause(generator: Generator, node: AnyNode) {
  node = catchClause.assert(node);
  catchClause.assert(node);
  generator.word('catch');
  + if (node.param) {
  generator.space();
  generator.token('(');
  generator.print(node.param, node);
  generator.token(')');
  + }
  generator.space();
  generator.print(node.body, node);
  }
  