Create database fails when an empty createDatabase folder is present

[theiam79]

Describe the bug
If an empty createDatabase folder exists, grate does not fall back to the default creation script, so no database is created.

To Reproduce
Create all default folders for grate, leaving createDatabase empty. Attempt to run a migration targeting a database that doesn't exist.

Expected behavior
The default creation script to be used (or clearer docs about which folders can be safely left empty)

Desktop (please complete the following information):

• OS: Windows 11
• Version: 1.7.4

Additional context
This isn't really a huge issue, as I mostly stumbled into it because I created the entire folder schema while testing the tool. I think making it work like the other folders (where they are ignored if empty) or clearly documenting that it is an exception would be fine.