We once again have a report of a panic from ParseRIB. This panic guard
should probably remain permanent.
Updates #14201
This reverts commit de9d4b2f886b6bf5cf0fe9be6c17d080267acef1.
Signed-off-by: James Tucker <james@tailscale.com>
(cherry picked from commit 80a100b3cb7033bbb0d8bc0846719430a8d37d99)