fix: Avoid a nil index crash when data loss occurs

[dljsjr]

Check all that apply

Type of Change

• [ ] WWST Certification Request
  • If this is your first time contributing code:
    • [ ] I have reviewed the README.md file
    • [ ] I have reviewed the CODE_OF_CONDUCT.md file
    • [ ] I have signed the CLA
  • [ ] I plan on entering a WWST Certification Request or have entered a request through the WWST Certification console at developer.smartthings.com
• [x] Bug fix
• [ ] New feature
• [ ] Refactor

Checklist

• [x] I have performed a self-review of my code
• [x] I have commented my code in hard-to-understand areas
• [x] I have verified my changes by testing with a device or have communicated a plan for testing
• [ ] I am adding new behavior, such as adding a sub-driver, and have added and run new unit tests to cover the new behavior

Description of Change

This fixes an edge case where we were assuming that a persistent field on a device was always present; while this should more or less hold true, there are times when it won't. In those cases, the driver would crash.

Drivers in this state would already be nonfunctional, but we want to avoid chewing up resources with a hot crash loop.

Summary of Completed Tests

I tested this locally by onboarding my Hue setup and then deliberaly taking actions that would lead to the persisted fields getting blown away; the driver is nonfunctional, but no longer hits a hot crash loop.

[github-actions[bot]]

Test Results

   62 files    383 suites   0s :stopwatch: 1 862 tests 1 862 :white_check_mark: 0 :zzz: 0 :x: 3 249 runs  3 249 :white_check_mark: 0 :zzz: 0 :x:

Results for commit b5cc4871.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

Minimum allowed coverage is 90%

Generated by :monkey: cobertura-action against b5cc4871177c422411f4ceef9cbd85056d5fe005

[varzac]

It's not obvious to me where the assumed key was causing a npe. Can you clarify where exactly that was happening?

[dljsjr]

@varzac It was a missing IP address, actually. This block was the cause of the original crash report: https://github.com/SmartThingsCommunity/SmartThingsEdgeDrivers/pull/1620/files#diff-5a04f9b727d9d403a969e8b24dff2d9162b47cd213254faf3f910be2697c24c4L252

The Application Key isn't the only "important" piece of data that can be lost, but it's the only one that's not easy to recover.

The other changes in this PR address other locations where we were trying to access Fields that could have been lost. They presented as additional crashes or pathological/resource consuming code paths that showed up after I fixed the initial crash.

[github-actions[bot]]

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