Telegram notifications aren't sent when using "system default" notification format

**Describe the bug** Notifications (to Telegram) cannot be sent via default configuration. It shows the error message `'NoneType' object has no attribute 'startswith'`. <img width="698" height="282" alt="Image" src="https://github.com/user-attachments/assets/70e21e5c-31ae-4d5f-a263-02b48d9a50a8" /> I assume this is where the issue is coming from: https://github.com/dgtlmoon/changedetection.io/blob/281c1ea7e171d38f2cbc5192fc475ebf7dbdb44b/changedetectionio/notification/handler.py#L59-L80 The reason is the "Notification format" setting. When creating a new monitor, it is set to "System default". That setting leads to the above error message. Changing it to "Text" will fix the issue. <img width="238" height="193" alt="Image" src="https://github.com/user-attachments/assets/af20c860-1240-4c68-aa0d-38adc42dcd59" /> **Version** v0.55.3 **How did you install?** Docker **To Reproduce** Steps to reproduce the behavior: 1. Set up a new monitor 2. Go to the notifications settings 3. Enter a valid Telegram apprise url 4. Click on "Send test notifications" **Expected behavior** The system default should work out of the box without errors. **Screenshots** See above **Desktop (please complete the following information):** - OS: [e.g. iOS] - Browser [e.g. chrome, safari] - Version [e.g. 22] **Smartphone (please complete the following information):** - Device: [e.g. iPhone6] - OS: [e.g. iOS8.1] - Browser [e.g. stock browser, safari] - Version [e.g. 22] **Additional context** Add any other context about the problem here.