Respond to CR.

Signal/src/network/PushManager.m

@@ -280,6 +280,7 @@ NSString *const Signal_Message_MarkAsRead_Identifier = @"Signal_Message_MarkAsRe
 {
     NSString *threadId = userInfo[Signal_Thread_UserInfo_Key];
     if (!threadId) {
+        OWSProdLogAndFail(@"%@ missing thread id for notification.", self.logTag);
         return;
     }