Remove mealy-mouthed isset check from params['id']

[eileenmcnaughton]

Overview

Remove isset to clarify that $params['id'] is either a value or NULL

Before

To get to this point

the code must pass through this try -catch

so we
a) know the array key exists
b) know that it is either NULL or an integer per the return values of $this->lookupContactID

After

Checking for truthy-ness makes it clear that if there is a value it is meaningful (not an empty string for example)

Technical Details

Comments

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[eileenmcnaughton]

Closing since #23531 will see this out