Backport of "BaseSrc, PushSrc: add nullable annotations to virtual methods" into 1.22
requested to merge tpm/gstreamer:backport-mr-3806-into-1.22-base_src_create_fix_annotation into 1.22
Backport of !3806 (merged) "BaseSrc, PushSrc: add nullable annotations to virtual methods".
Commits:
- c8298a27 BaseSrc, PushSrc: add nullable annotations to virtual methods