Remove base schema if initialization from db fails

If user tries to init from database, but for some reason init fails, another try to do init will result in a confusing error:
```
Base schema exists but missing which project it belongs to
```
As a fix, we should remove partially created base schema so that we don't have half-initialized data in the database.

Related to #90 (but this is init from DB rather than init from GPKG)