The fix for generates a default constraint name used only for creating DDL if no name is provided. In this case the value returned by Constraint.getName() will be null (not the generated name).
This generate name is based on the columns making up the constraint, so the generated name will not be correct until after all columns are added to the constraint. Because the the constraint columns are not passed to the constructor, the name cannot be generated when the constraint is created.
We should revisit how/when columns are added and how/when the constraint name is generated to see if this can be simplified.