fix: properly handle loop then (#224)

Author: alangpierce

src/mappers/mapWhile.ts

@@ -14,7 +14,7 @@ export default function mapWhile(context: ParseContext, node: CoffeeWhile): Whil
   if (startToken && startToken.type === SourceType.LOOP) {
     return new Loop(
       line, column, start, end, raw,
-      node.body ? mapAny(context, node.body) : null
+      mapPossiblyEmptyBlock(context, node.body)
     );
   }
 

test/examples/empty-loop/input.coffee

@@ -0,0 +1 @@
+loop then

test/examples/empty-loop/output.json

@@ -0,0 +1,34 @@
+{
+  "body": {
+    "column": 1,
+    "inline": false,
+    "line": 1,
+    "range": [
+      0,
+      4
+    ],
+    "raw": "loop",
+    "statements": [
+      {
+        "body": null,
+        "column": 1,
+        "line": 1,
+        "range": [
+          0,
+          4
+        ],
+        "raw": "loop",
+        "type": "Loop"
+      }
+    ],
+    "type": "Block"
+  },
+  "column": 1,
+  "line": 1,
+  "range": [
+    0,
+    10
+  ],
+  "raw": "loop then\n",
+  "type": "Program"
+}