Fix wasm2wat demo (#2722)

This was broken by #2721

Author: kevmoo

docs/demo/wasm2wat/demo.js

@@ -55,7 +55,9 @@ editorContainer.ondrop = function(e) {
     return;
   }
   readAndCompileFile(file);
-} let fileBuffer = null;
+};
+
+let fileBuffer = null;
 renderFeatures(wabt, features, () => {
   saveLocalStorageFeatures(features);
   compile(fileBuffer);