Article 3917569 has Source with missing source_text

[mircealungu]

Bug

Article ID 3917569 causes a crash when trying to open it:

File "/Users/gh/zeeguu/api/zeeguu/core/model/source.py", line 46, in get_content
    return self.source_text.content
AttributeError: 'NoneType' object has no attribute 'content'

Cause

The article has a source_id pointing to a Source record, but that Source's source_text_id is NULL or points to a non-existent SourceText.

Investigation needed

1. Check the Source record linked to this article
2. Determine how this data inconsistency occurred
3. Either fix the data or mark the article as broken

Temporary workaround

A defensive null check was added in PR #441, but this masks the real issue rather than fixing it.

Reproduce

Visit: /read/article?id=3917569