core: move skip to stream

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
tests: add NULL test for stream

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>
core: stream: fix SEGV + add cache

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>