Ref #967: Add queue parsing check in heartbeat

[leplatrem]

Related to #967

And Graham's comment https://github.com/mozilla/jira-bugzilla-integration/pull/961#discussion_r1574887084

[sentry-io[bot]]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ InterruptedError: [Errno 4] Interrupted system call: '/var/lib/jbi/queue/1881525' /__heartbeat__ View Issue

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