fix(dispatcher): resp.json(silent=) 是 Flask API，requests 不支持会抛 TypeError

Edge 返回结果解析时 TypeError 逃逸到轮询循环，任务卡死 PROCESSING

fam-core/src/fam_core/dispatcher/dispatcher.py

@@ -114,7 +114,10 @@ class Dispatcher:
             self._schedule_retry(task)
             return
 
-        result = resp.json(silent=True) or {}
+        try:
+            result = resp.json()
+        except ValueError:
+            result = {}
         if result.get('status') == 'success':
             try:
                 event_id = apply_success_event(task_id, result)