wrench create behavior changed to return error with empty schema file

[asetty]

Expected Behavior

I expected the database to be created with no tables other than the migration table. This used to be the behavior before migration to memefish

Current Behavior

Error command: create, version: v1.11.1
Failed to execute the operation to Cloud Spanner, DDL statement is empty.

Steps to Reproduce

Run wrench create with empty schema.sql file

Context (Environment)

• wrench version: 1.11.1
• spanner emulator

There is a simple fix to check for empty strings when parsing the DDL I will post a PR for.