[runwhen-local-feedback] Scan error handling when branch ref or meta file doesn't exist

[stewartshea]

Observation
We can run into some scenarios where the referenced troubleshooting code might not exist, or it exists and has no meta.yaml associated with it.

Request failed with status code: 404
Traceback (most recent call last):
  File "/workspace-builder/run.py", line 441, in <module>
    main()
  File "/workspace-builder/run.py", line 353, in main
    cheatsheet.cheat_sheet(output_path)
  File "/workspace-builder/cheatsheet.py", line 693, in cheat_sheet
    interesting_commands = search_keywords(parsed_robot, parsed_runbook_config, search_list, meta)
  File "/workspace-builder/cheatsheet.py", line 213, in search_keywords
    for cmd_meta in meta['commands']:
TypeError: 'NoneType' object is not subscriptable

Possible Suggestions
We need to add in some checking and default content here to keep building the documentation even when the file is not accessible.

Any other details or context