fix(sftp): Handle empty port parameter to allow host-defined ports

[solracsf]

Fix #58324
Fix #58293

Summary

Regression from #57793

When a host string includes a port (e.g., 1.2.3.4:22), it was being ignored if $parameters['port'] was present but empty (e.g., ''). The previous logic $parameters['port'] ?? $parsedHost[1] treated an empty string as a valid value, overriding the port correctly parsed from the host.

This fix ensures $parameters['port'] is only prioritized if it contains a valid numeric value. Empty strings, nulls, or non-numeric values now correctly fall back to the port defined in the host string.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[solracsf]

/backport to stable33

[solracsf]

/backport to stable32

[solracsf]

/backport to stable31

[tgeller]

Tested and it seems to work.

See https://help.nextcloud.com/t/file-access-syncing-broken-typeerror-fsockopen-argument-2-port-must-be-of-type-int-string-given/240346 .