When creating a project, primary slug is generated by project name.
If same as primary tag is added in "Additional Hashtags' field, exception is thrown.

Steps to reproduce:

1. Open "create project" page.
2. Input same single word value to Name and Additional Hashtags fields.
3. Click Save.

Result:

Unhandled Exception ("AphrontDuplicateKeyQueryException")
#1062: Duplicate entry 'xyz' for key 'key_slug'

Expected result:
Project created and tag ignored silently. Tag will appear in project hashtags list still, because it will be created by name.