This crept in as part of the MRIB improvements and I missed the compiler
warning between other noise. Unfortunately, printing an uninitialised
variable can in fact make zebra crash, so this is not trivial.
Fixes: 3b02fe8 ("zebra: add "show ip rpf" to get result of RPF lookup")
Signed-off-by: David Lamparter <firstname.lastname@example.org>