[Create Profile Edge Case] Users with the profile created can still access `/create`

[cunbidun]

Describe the bug
Users with the profile created can still access /create.

To Reproduce
Steps to reproduce the behavior:

1. Login.
2. Go to /create.

Expected behavior
Users with a profile should not have access to /create because when they submit a new profile creation form, the server always returns an error status.

Suggested Solution
When a user login, the server can respond with a boolean variable to show the user already has a profile or not.