fix excessive whitespace trimming resulting in innaccurate sourcemap line - fixes #151

test/fixtures/transformation/array-comprehension/multiple/expected.js

@@ -2,10 +2,8 @@
 
 var arr = (function () {
   var _arr = [];
-
   for (var _iterator = "abcdefgh".split("")[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
     var x = _step.value;
-
     for (var _iterator2 = "12345678".split("")[Symbol.iterator](), _step2; !(_step2 = _iterator2.next()).done;) {
       var y = _step2.value;
       _arr.push(x + y);