fix: 修复非 Node 环境报错

Author: xream

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "sub-store",
-  "version": "2.20.46",
+  "version": "2.20.47",
   "description": "Advanced Subscription Manager for QX, Loon, Surge, Stash and Shadowrocket.",
   "main": "src/main.js",
   "scripts": {

backend/src/vendor/express.js

@@ -9,8 +9,9 @@ export default function express({ substore: $, port, host }) {
         'Access-Control-Allow-Methods': 'POST,GET,OPTIONS,PATCH,PUT,DELETE',
         'Access-Control-Allow-Headers':
             'Origin, X-Requested-With, Content-Type, Accept',
-        'X-Powered-By':
-            eval('process.env.SUB_STORE_X_POWERED_BY') || 'Sub-Store',
+        'X-Powered-By': isNode
+            ? eval('process.env.SUB_STORE_X_POWERED_BY') || 'Sub-Store'
+            : 'Sub-Store',
     };
 
     // node support