Fix a sad bug

src/assets/environments/environments.js

@@ -5,7 +5,8 @@ const BASE_ENVIRONMENTS = [
   "/rooms/rooftopbuilding1/RooftopBuilding1.bundle.json",
   "/rooms/wideopenspace/WideOpenSpace.bundle.json"
 ];
-const ALL_ENVIRONMENTS = (process.env.EXTRA_ENVIRONMENTS || "").split(",").concat(BASE_ENVIRONMENTS);
+const EXTRA_ENVIRONMENTS = process.env.EXTRA_ENVIRONMENTS ? process.env.EXTRA_ENVIRONMENTS.split(",") : [];
+const ALL_ENVIRONMENTS = EXTRA_ENVIRONMENTS.concat(BASE_ENVIRONMENTS);
 
 export const ENVIRONMENT_URLS = ALL_ENVIRONMENTS.map(x => process.env.ASSET_BUNDLE_SERVER + x);
 export const DEFAULT_ENVIRONMENT_URL = ENVIRONMENT_URLS[0];