Merging existing tags error when data.tags is not present

[epipav]

Changes proposed ✍️

What

🤖 Generated by Copilot at e1574f5

Fix a bug in organizationRepository.ts that overwrites organization tags. The change prevents losing existing tags when updating an organization's profile.
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🤖 Generated by Copilot at e1574f5

tags undefined?
Use empty array instead
Preserve old values

Why

How

🤖 Generated by Copilot at e1574f5

• Fix bug of overwriting organization tags when updating profile (link)

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screenshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.