ng_pipe: Do not panic when memory allocations fail
Signed-off-by: Martin Vahlensieck <git@academicsolutions.ch>
Reviewed by: markj
MFC after: 2 weeks
Pull Request: https://github.com/freebsd/freebsd-src/pull/1181
(cherry picked from commit d44c78074d8738db67a2fa6bf07b630c61eee6ab)