Nothing happens when creating the first superadmin user

Describe the bug

When submitting the "create superadmin" form, nothing happens.

Steps to reproduce

1. Install Castopod
2. On the superadmin creation form, enter the first superadmin info with a simple password, eg. hello
3. Submit the form
4. Nothing happens

Expected behavior

The superadmin should be created or an error should appear.

Context

• Castopod: 1.0.0-beta.5

Possible fixes

The message block is missing in the install form, rendering system feedback impossible. --> Add the message block!