Add missing check for moderator CB id

[amCap1712]

AFAIU this situation should only happen if a moderator does not have a CB account. Since, we have StrictDefined mode on we need the is defined check first. Found in local development.

[github-actions]

Unit Test Results

    1 files  ±0      1 suites  ±0   1m 15s ⏱️ -5s
156 tests ±0  156 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 62cf3c8. ± Comparison against base commit 387a841.

[alastair]

this is fine, but it probably doesn't need the final and mod[]... If the item is missing if there is no cb_id, but present and filled in if there is, then just the defined check should be enough.