fix(client): propagate SASS parser errors from worker

client/src/client/workers/sass-compile.js

@@ -3,6 +3,10 @@ import Sass from 'sass.js';
 onmessage = e => {
   const data = e.data;
   Sass.compile(data, result => {
+    if (result.status === 0) {
       self.postMessage(result.text);
+    } else {
+      throw result.formatted;
+    }
   });
 };