'restock' is undefined

[geekho-me]

Describe the bug
When you have a global Notification Body configured which includes restock.price and/or restock.original_price; if you send a notification from a standard Webpage Text/HTML, JSON and PDF changes detection, the notification fails to send with the notification error:

Notification Log:

SENDING - null
'restock' is undefined

Version
v0.50.21

How did you install?

Docker

To Reproduce

Steps to reproduce the behavior:

1. Go to SETTINGS
2. Click on Notifications
3. Set Notification Title to: {{watch_title}}
4. Set Notification Body to:

{
  "base_url": {{base_url|default('')|tojson}},
  "watch_url": {{watch_url|default('')|tojson}},
  "watch_uuid": {{watch_uuid|default('')|tojson}},
  "watch_title": {{watch_title|default('')|tojson}},
  "watch_tag": {{watch_tag|default('')|tojson}},
  "preview_url": {{preview_url|default('')|tojson}},
  "diff_url": {{diff_url|default('')|tojson}},
  "diff": {{(diff or '')[:3500]|tojson}},
  "diff_added": {{(diff_added or '')[:3500]|tojson}},
  "diff_removed": {{(diff_removed or '')[:3500]|tojson}},
  "diff_full": {{(diff_full or '')[:3500]|tojson}},
  "diff_patch": {{(diff_patch or '')[:3500]|tojson}},
  "current_snapshot": {{(current_snapshot or '')[:3500]|tojson}},
  "triggered_text": {{triggered_text|default('')|tojson}},
  "restock_price": {{restock.price|default('')|tojson}},
  "restock_original_price": {{restock.original_price|default('')|tojson}}
}

5. Set Notification format to: Text
6. Press Save button
7. Recheck your default Hacker News detection (https://news.ycombinator.com/) to trigger a detection
8. Error occurs

Expected behavior

Successfully send a notification

Screenshots

Additional context
I suppose this is somewhat expected to happen as the check is not a restock check; however it would be useful to have these fields default to null so you do not need custom notifications per check.

[dgtlmoon]

ahh thanks for this

[dgtlmoon]

note to self - yeah the restock data should be stored in its own .json in the watch data dir

[dgtlmoon]

related/duplicate of #2600