Using Query.setParamater("param", null) on some datatypes (not all, or even most) gives the following error from the database.

column "the_array" is of type bigint[] but expression is of type bytea

I have found a solution that works for me, but it needs to be tested for more database types, not just PostgreSQL, and I don't have the set-up for that. I will submit it once I have an issue number.
It is a workaround to what might get fixed in the JDBC driver or even the database itself, but those are typically updated less often in a project.