Fix writing collections where first element is null

[tamland]

This is a fix for #2215. It is unclear to me what the code checking the class of the first element is supposed to solve as there appear to be no tests covering its behavior.

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[tamland]

@mp911de / @schauder Could you have a look at this? We are unable to upgrade from spring boot 3.4 due to this issue

[schauder]

When rebased against current main the test you added does not work with Postgres. Also saveAndLoadListOfDirectionAsArray fails with Postgres.

To run all tests using Postgres as the database run ./mvnw clean verify -Dspring.profiles.active=postgres

To run all tests with all databases run ./mvnw clean verify -Pall-dbs

Let us know if you want to keep working on this PR, or if we should close it.

[tamland]

@schauder Thanks, I was just running the default test config which clearly didn't do anything.

I have updated the PR to at least fix the issue for simple array types. However, I am unable find a good solution for EntityWithDirections where custom enum converter are used.

[schauder]

That is unfortunate.
Thanks for trying.