disable-repo-locking crashes the server

[kbaldyga]

v0.17.0_now panics when disable-repo-locking is enabled.

2021/05/04 10:39:40 PANIC: runtime error: invalid memory address or nil pointer dereference
goroutine 38 [running]:
github.com/urfave/negroni.(*Recovery).ServeHTTP.func1(0x7fb2d452c438, 0xc00000e3e8, 0xc000078af0, 0xc0004e3000)
	/go/pkg/mod/github.com/urfave/[email protected]/recovery.go:159 +0xd2
panic(0x11d40e0, 0x1cb4ee0)
	/usr/local/go/src/runtime/panic.go:965 +0x1b9
github.com/runatlantis/atlantis/server.(*Server).Index(0xc0004d96c0, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3200)
	/home/circleci/project/server/server.go:744 +0x4d9
net/http.HandlerFunc.ServeHTTP(0xc0004b27c0, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3200)
	/usr/local/go/src/net/http/server.go:2069 +0x44
github.com/gorilla/mux.(*Router).ServeHTTP(0xc0004de240, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000)
	/go/pkg/mod/github.com/gorilla/[email protected]/mux.go:210 +0xd3
github.com/urfave/negroni.Wrap.func1(0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000, 0xc00006ce20)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:46 +0x4d
github.com/urfave/negroni.HandlerFunc.ServeHTTP(0xc00000c408, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000, 0xc00006ce20)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:29 +0x4e
github.com/urfave/negroni.middleware.ServeHTTP(0x15c6a80, 0xc00000c408, 0xc00000c450, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:38 +0x9c
github.com/runatlantis/atlantis/server.(*RequestLogger).ServeHTTP(0xc0004b3db0, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000, 0xc00006ce00)
	/home/circleci/project/server/middleware.go:36 +0x1a4
github.com/urfave/negroni.middleware.ServeHTTP(0x15c4040, 0xc0004b3db0, 0xc00000c438, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:38 +0x9c
github.com/urfave/negroni.(*Recovery).ServeHTTP(0xc000078af0, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000, 0xc00006cde0)
	/go/pkg/mod/github.com/urfave/[email protected]/recovery.go:193 +0x8c
github.com/urfave/negroni.middleware.ServeHTTP(0x15c4720, 0xc000078af0, 0xc00000c420, 0x7fb2d452c438, 0xc00000e3e8, 0xc0004e3000)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:38 +0x9c
github.com/urfave/negroni.(*Negroni).ServeHTTP(0xc0001603c0, 0x15d94a8, 0xc0001008c0, 0xc0004e3000)
	/go/pkg/mod/github.com/urfave/[email protected]/negroni.go:96 +0xf1
net/http.serverHandler.ServeHTTP(0xc00013a000, 0x15d94a8, 0xc0001008c0, 0xc0004e3000)
	/usr/local/go/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc0000b34a0, 0x15ddcf0, 0xc0004fe900)
	/usr/local/go/src/net/http/server.go:1952 +0x8cd
created by net/http.(*Server).Serve
	/usr/local/go/src/net/http/server.go:3013 +0x39b

This seems to be related to #1473, the applyLockingClient is not initialised in the branch resposible for disabling-repo-lock https://github.com/runatlantis/atlantis/blame/79309ed39c21c06bd8a8dea7e7c8802e4b15313c/server/server.go#L303

[gezb]

@acastle would it be possible to get a v0.17.1 release with this fix backported?

[kmannuz]

Seeing this error as well on v0.17.0