msg: Remove unnecessary call of nlmsg_free on known NULL pointer
msg: Remove unnecessary call of nlmsg_free on known NULL pointer

In nlmsg_convert, if __nlmsg_alloc fails we can return NULL directly
instead of unnecessarily calling nlmsg_free on the NULL pointer.

Signed-off-by: Tobias Klauser <9249c549618448e4c699e8032ba6c7f0d7fd4b7f@distanz.ch>
Acked-by: Thomas Graf <17c2d8920621522552b392f72d8fdb4d1e866b44@suug.ch>
Signed-off-by: Thomas Haller <16e26612e4159990a6b3691e92592e691ff74132@redhat.com>

cfriedt/libnl,claudelee/libnl,vyos/libnl3,congwang/libnl,vyos/libnl3,honsys/libnl,tgraf/libnl,greearb/libnl-ct,houstar/libnl,greearb/libnl-ct,mshirley/libnl,tklauser/libnl,kolyshkin/libnl,houstar/libnl,claudelee/libnl,thom311/libnl,HolyShitMan/libnl-1,claudelee/libnl,greearb/libnl-ct,tgraf/libnl,vyos/libnl3,HolyShitMan/libnl-1,kolyshkin/libnl,baloo/libnl,cyclops8456/libnl3,dsahern/libnl,UnicronNL/libnl3,thom311/libnl,honsys/libnl,UnicronNL/libnl3,cfriedt/libnl,congwang/libnl,cyclops8456/libnl3,claudelee/libnl,tklauser/libnl,HolyShitMan/libnl-1,tgraf/libnl,kolyshkin/libnl,baloo/libnl,UnicronNL/libnl3,cyclops8456/libnl3,mshirley/libnl,UnicronNL/libnl3,honsys/libnl,tklauser/libnl,congwang/libnl,houstar/libnl,honsys/libnl,tgraf/libnl,tklauser/libnl,cfriedt/libnl,HolyShitMan/libnl-1,mshirley/libnl,cfriedt/libnl,dsahern/libnl,baloo/libnl,vyos/libnl3,congwang/libnl,kolyshkin/libnl,cyclops8456/libnl3,houstar/libnl,dsahern/libnl,dsahern/libnl,mshirley/libnl,thom311/libnl,baloo/libnl