"The select expression is not a valid expression" is thrown when creating a user

[jonjomckay]

The following error is thrown when trying to create a new user:

An exception occurred while creating a query in EntityManager:
Exception Description: Syntax error parsing [select exists (select ?1
from UserTable userTable
where userTable.email = ?2)
from UserTable userTable].
[7, 76] The select expression is not a valid expression.

It looks like QueryDSL is creating an incorrect SQL query from the given statements.