Only migrate up if no import.
Only migrate up if no import.

As well as being more efficient, this actually stops a bug where a import is a few versions behind the current version of code.
Table is created in the migration, not deleted by the import, then the migration tries to run and create the table again and errors!

[skip-ci]

SlightScribe/SlightScribe-Core,SlightScribe/SlightScribe-Core,SlightScribe/SlightScribe-Core