4001d0bf25 caused tests in another repo to fail with a crash, calling
a nil func. This might not be the right fix, but fixes the build.
Change-Id: I67263f883c298f307abdd22bc2a30b3393f062e6
Co-authored-by: Maisem Ali <maisem@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>