Cannot process PR without repo

[gaschler]

Wally segfaults with nil pointer dereference in

github.com/googlecartographer/infrastructure/wally_the_cartographer/cmd.checkoutRemoteBranch(0xc4205fe000, 0xc4200188e8, 0x4, 0xa901e0, 0xc42000e018, 0xc4205db310, 0x6, 0xc42041b2f0, 0x90, 0xc420750090)
go/src/github.com/googlecartographer/infrastructure/wally_the_cartographer/cmd/root.go:178 +0x73
github.com/googlecartographer/infrastructure/wally_the_cartographer/cmd.keepPRPristine(0xc42027a000, 0xc4205fe000, 0xc4200188e8, 0x4, 0xa901e0, 0xc42000e018, 0x0, 0x0, 0x0, 0x0)
go/src/github.com/googlecartographer/infrastructure/wally_the_cartographer/cmd/root.go:313 +0x239
github.com/googlecartographer/infrastructure/wally_the_cartographer/cmd.handleRepo(0xa941c0, 0xc4200180e0, 0xc420104d80, 0xc4205a8680, 0x16, 0x275fd2, 0xc420014420, 0x23, 0xc4200188e8, 0x4, ...)

in line
https://github.com/googlecartographer/infrastructure/blob/ef46707312aa83c395aef3cfcfd07e6b32f78010/wally_the_cartographer/cmd/root.go#L178

because branch.Repo is nil
while handling a PR that has no upstream repository (cartographer-project/cartographer_ros#773).

I guess the expected behavior is to skip PRs without upstream repository and proceed.

[ojura]

Hahah, sorry for taking Wally out :-) Accidentally pushed a private branch to the public repo, so I had to recreate it.