`pullUpInterface`'s `portUniquify` should provide `null` physical port instead of throw exceptions when non-single port mapping exists

### Motivation

Currently, if there are 0 or >1 logical ports mapped to an interface, then the `portUniquify` function can't be called since it only works with exactly 1 physical port present. This is annoying if there are multiple physical ports or no physical ports mapped to at least one logical port, but you don't need to use the physical name for uniquification.

### Desired solution

Rather than throwing an exception, it would be nice to just make the function signature provide `null` for cases where there isn't exactly one physical port mapping. Then logical uniquification can still be done.

### Alternatives considered

_No response_

### Additional details

_No response_