fix: handle nil OAuth application in commits API

What does this MR do and why?

Fixes a 500 internal server error when creating commits through the API using OAuth password grant tokens (where application is nil).

The web_ide_request? helper method attempted to call .id on access_token.application without checking if it was nil first. This caused a when using an oauth token with application being nil.

While the commit was successfully created, the API returned a 500 error instead of 201, breaking client integrations and CI/CD pipelines.

References

Closes #569048

How to set up and validate locally

1. Start your GDK instance
2. Get an OAuth token using password grant:

export GITLAB_TOKEN=$(curl -sS --data "grant_type=password&username=root&password=YOUR_PASSWORD" --request POST "http://<your_gdk_url>/oauth/token" | jq -r .access_token)

3. Create a commit using that token:

curl -X POST "http://<your_gdk_url>/api/v4/projects/:id/repository/commits" -H "Authorization: Bearer $GITLAB_TOKEN" -H "Content-Type: application/json" -d '{"branch": "<your_branch>", "commit_message": "Test commit", "actions": [{"action": "create", "file_path": "test.txt", "content": "test"}]}'

4. Verify you get a 201 Created response (not 500 internal server error message)

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