check if latest_comment_url is valid when processing gh notifications

[danlipert]

Description

Prevents sentry alert when github notifications do not have a valid latest_comment_url

Checklist

• Read and conforms to the contributor guidelines
• Read and conforms to the style guidelines
• Linter status: 100% pass
• Added relevant tests
• Tests pass and code coverage has not decreased
• Changes don't break existing behavior
• Commit message follows commit guidelines
• Code documentation
• Completed: Code review by core team and any requested changes

Affected core subsystem(s)

gitcoinbot

Testing and Sign-off

the split call on latest_comment_url usually throws an unhandled exception, so this change prevents that by continuing to loop over the notifications before getting to the split call

Contributor

• Read and followed the Contributor Guidelines
• Tested all changes locally
• Verified existing functionality
• Ran make test and everything passed!

Reviewer

• Affirm contributor guidelines have been followed and requested changes made
• CI tests and linting pass
• No conflicts (migrations, files, etc)
• Regression tested against staging or local deployment

[codecov]

Codecov Report

Merging #4136 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #4136      +/-   ##
==========================================
- Coverage   30.37%   30.37%   -0.01%     
==========================================
  Files         206      206              
  Lines       16401    16404       +3     
  Branches     2155     2156       +1     
==========================================
  Hits         4982     4982              
- Misses      11239    11242       +3     
  Partials      180      180

Impacted Files	Coverage Δ
...itcoinbot/management/commands/get_notifications.py	0% <0%> (ø)	⬆️

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[octavioamu]

LGTM