message: add expression visiting for exception var
diff: @@ -1805,6 +1805,9 @@ export class TryCatchStatement extends Statement {
  walk(this, 'tryBranch', visitor, options);
  walk(this, 'catchBranch', visitor, options);
  }
  + if (this.exceptionVariable && options.walkMode & InternalWalkMode.walkExpressions) {
  + walk(this, 'exceptionVariable', visitor, options);
  + }
  }
  }
  