teleport proxy crash

[klizhentas]

Description

Teleport proxy can sometimes crash.

Versions affected:

Teleport >= 2.2.3

Relevant lines:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0xd45193]
goroutine 1501 [running]:
github.com/gravitational/teleport/lib/srv.(*proxySubsys).proxyToSite(0xc4213ce070, 0x0, 0x0, 0x1845340, 0xc42132e390, 0x184d800, 0xc4207b2000, 0x7fae03456c20, 0xc4213ce070)
    /gopath/src/github.com/gravitational/teleport/lib/srv/proxy.go:171 +0x63
github.com/gravitational/teleport/lib/srv.(*proxySubsys).start(0xc4213ce070, 0xc421f02360, 0x184d800, 0xc4207b2000, 0xc42128e800, 0xc4219da0e0, 0x7fae03456c20, 0xc422202c58)
    /gopath/src/github.com/gravitational/teleport/lib/srv/proxy.go:159 +0x4a8
github.com/gravitational/teleport/lib/srv.(*Server).handleSubsystem(0xc4205c0e00, 0x184d800, 0xc4207b2000, 0xc42128e800, 0xc4219da0e0, 0x2, 0xc42006f400)
    /gopath/src/github.com/gravitational/teleport/lib/srv/sshserver.go:1049 +0x24f
github.com/gravitational/teleport/lib/srv.(*Server).dispatch(0xc4205c0e00, 0x184d800, 0xc4207b2000, 0xc42128e800, 0xc4219da0e0, 0xc421fa4e20, 0x28)
    /gopath/src/github.com/gravitational/teleport/lib/srv/sshserver.go:915 +0x2bc
github.com/gravitational/teleport/lib/srv.(*Server).handleSessionRequests(0xc4205c0e00, 0xc421f02360, 0x184d800, 0xc4207b2000, 0xc4219b4000)
    /gopath/src/github.com/gravitational/teleport/lib/srv/sshserver.go:886 +0x2e5
created by github.com/gravitational/teleport/lib/srv.(*Server).HandleNewChan
    /gopath/src/github.com/gravitational/teleport/lib/srv/sshserver.go:722 +0x29c