fixes for a couple exceptions caught in the logs

[diosmosis]

Description:

Changes:

• If UrlFetchApp throws an exception with what is likely a temporary error, retry the request.
• If UrlFetchApp returns no responses, and fetch() returns undefined, retry the request.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed