This regression was introduce by fix for making buffer pool thread safe. When we renegotiate, the pool will be setup after we set the format. But the code has been simplified to only get the pool once before, which caused a null pointer deref. Fixes 94ba019 ("v4l2: Fix SIGSEGV on 'change state' during 'format change'") Related to !3481 Fixes #1626 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3513>