Bug: Cannot create new Vendor with email.

Every time I try and create a new vendor with an email address an exception gets thrown.
I am using the latest build on master from the Github repo.
Creating a vendor without an email, or duplicating a vendor, works just fine.

This is the error:
Uncaught TypeError: Cannot read property 'toLowerCase' of undefined
at HTMLDocument.eval (eval at (eval at ExRmtSvrCd (sessionCtrl.js:833)), :1:29319)
/akaunting/purchases/vendors:1 Failed to load resource: the server responded with a status of 500 ()

I ran the app in debug mode and it is an SQL error:
LOG.error: SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for integer: "" (SQL: select count(*) as aggregate from "yen_contacts" where "email" = [email protected] and "id" <> and "company_id" = 1 and "type" = vendor and "deleted_at" is null) {"userId":1,"exception":{"errorInfo":["22P02",7,"ERROR: invalid input syntax for integer: \"\""]}}

I am using postgresql, not sure if that has anything to do with it.