优化获取平台币接口coin返回null的问题

server/app/api/controller/UserController.php

@@ -147,7 +147,7 @@ class UserController extends OpenController
         if (empty($user)) {
             return $this->fail('缓存已过期，请重新登录', ReturnCode::TOKEN_TIMEOUT);
         }
-        $coin = $user['coin'] ?? null;
+        $coin = $user['coin'] ?? 0;
         if (is_string($coin) && is_numeric($coin)) {
             $coin = str_contains($coin, '.') ? (float) $coin : (int) $coin;
         }