Potential fix for code scanning alert no. 5574: Dereferenced variable is always null

[ChristianRosewich]

Potential fix for https://github.com/ChristianRosewich/CSharp/security/code-scanning/5574

To fix this safely without changing behavior, replace the null-prone comparison on line 907:

• from: dB_EventTable.Fields[EventFields.Art].AsEnum<EEventArt>() == text.AsEnum<EEventArt>()
• to: dB_EventTable.Fields[EventFields.Art].AsEnum<EEventArt>() == eArt

This is the best fix because:

• it removes a guaranteed-null dereference risk,
• it uses the already-available strongly typed enum variable (eArt) that is already used for the indexed seek in the same block,
• it preserves intended filtering logic (match current record art to selected eArt).

Also remove the now-unused text declaration at line 806 to keep the method clean and avoid warnings.

Suggested fixes powered by Copilot Autofix. Review carefully before merging.