Load active visits widget only when Location is defined

When fetching active visits with the `location` parameter as undefined, the backend throws the 404 error. Fetch the active visits only when the `location` parameter is defined.

Package: patient-management/packages/esm-active-visits-app

When the home page loads after the first login, it takes time to fetch the `session` details from the backend. The active visits are fetched with the location parameter as undefined the following error occurs: