TypeError: r.replace is not a function when merging contacts

Describe the bug

TypeError: r.replace is not a function when merging contacts

Description:
When attempting to merge two contacts, the merge operation gets stuck with a JavaScript error:
TypeError: r.replace is not a function

This appears in Merging.vue when the code tries to process contact property values that are null or non-string types.

Version: Nextcloud Contacts 8.3.0
Nextcloud: 32.0.3

Steps to reproduce:

1. Select two contacts to merge
2. Click merge button
3. Operation never completes and shows this error in browser console

Suggested fix:
Add null/type checking in the getPropertyValue() method or sanitize values before displaying them in the merge interface.

Steps to reproduce

Steps to reproduce:

Select two contacts to merge
Click merge button
Operation never completes and shows this error in browser console

Expected behavior

Contact should merge

Actual behavior

Contact don't merge

Contact version

No response

Operating system

No response

PHP engine version

None

Web server

None

Database

None

Additional info

No response

Start in Merging.vue and inspect the getPropertyValue() method, focusing on contact values that are null or non-string types. Reproduce the merge with two contacts and verify that the merge completes without the r.replace error and displays contact properties correctly.