Fix validation error when XML BOM declares multiple namespaces

[philippn]

Description

This PR contains a bugfix for gh-4008. I have also added a testcase, which was created by copying the bom-1.xml from another testcase.

Addressed Issue

The commit fixes a validation error that occurs when multiple namespace declarations are present in the BOM (in the wrong order).

Additional Details

n/a

Checklist

• I have read and understand the contributing guidelines
• This PR fixes a defect, and I have provided tests to verify that the fix is effective
• This PR implements an enhancement, and I have provided tests to verify that it works as intended
• This PR introduces changes to the database model, and I have added corresponding update logic
• This PR introduces new or alters existing behavior, and I have updated the documentation accordingly

[nscuro]

Thanks!

(The test failures are unrelated to your change)