test: add tests of nil/NULL support

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Add support for nil/NULL in out of band query parameters

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Dedup out of band query parameter handling

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>