Contact merge can auto-populate unrelated company

When merging contacts, if the company field is empty the merge flow can automatically add a company that is unrelated to the contacts being merged.

Observed in the same merge workflow where other contact-merge issues were reported, but this should be tracked separately from the merge-page 404 problem.

Reference examples from the original report:

• Easton Homes profile 1
• Easton Homes profile 2
• Bronze Door profile 1
• Bronze Door profile 2

Current behavior: when there is no company selected, the merge flow can choose and populate a company that has nothing to do with the records being merged.

Expected behavior: if no valid shared company can be inferred, the field should remain empty and never auto-populate an unrelated company.