iOS: SQLite error from writing to core data

I'm getting these errors from writing to core data and I'm not sure how to debug this.

Unknown error calling sqlite3_step (19: NOT NULL constraint failed: changes.customer_id) eu DB Query: INSERT INTO changes (value, customer_id, org_scope) VALUES (?, ?, ?)
Unknown error finalizing or resetting statement (19: NOT NULL constraint failed: changes.customer_id) DB Query: INSERT INTO changes (value, customer_id, org_scope) VALUES (?, ?, ?)