fix: avoid undefined community breadcrumb lookup

[dvd233]

References

Fixes #6168

Description

When opening the top-level community creation route, the community breadcrumb resolver is configured with breadcrumbQueryParam: 'parent', but no parent query parameter is present. The resolver currently falls back to the route id, which is also absent on /communities/create, and requests the REST endpoint with undefined.

Return an empty breadcrumb result when the optional parent parameter is absent. Existing community routes and sub-community creation routes continue to resolve their breadcrumbs normally.

Instructions for Reviewers

List of changes in this PR:

• Skip the community data lookup for top-level community creation.
• Add resolver coverage for normal routes, parent-community creation, and top-level creation.

To verify:

• Open New → Community as an administrator.
• Confirm that creating a top-level community does not issue a request to /api/core/communities/undefined.
• Confirm that creating a sub-community still loads the parent breadcrumb.

Testing

• TypeScript semantic check for the resolver and regression spec.
• Resolver branch harness: baseline fails on the top-level route; the fix passes all three route cases.
• Prettier check for the changed files.
• git diff --check.

The full repository npm test suite was not run locally because the dependency tree is not installed in this environment; CI should run the repository's standard checks.

[lgeggleston]

Hi @dvd233, thanks for your first contribution to DSpace. Since the issue was submitted recently, @MMilosz would you be willing to take a quick look at this fix maybe?

One note on the DSpace GitHub process for future PRs: we encourage you to comment on the issue (in this case, #6168) when you start working on it, ideally before submitting a PR. This allows us to assign the issue to you, check if there are any blockers, and avoid multiple people accidentally working on the same issue. Thanks!