debug-log EOF: invalid tag and panic seen in state server logs

I noticed in state server machine-0.log. I looked there because debug-log was failing with an EOF error. I think the panic below is the cause of that.

2015-06-03 02:01:32 DEBUG juju.worker.logger logger.go:45 reconfiguring logging from "<root>=DEBUG" to "<root>=WARNING;unit=DEBUG"
2015-06-03 02:01:33 WARNING juju.cmd.jujud machine.go:885 determining kvm support: INFO: Your CPU does not support KVM extensions
KVM acceleration can NOT be used
: exit status 1
no kvm containers possible
2015-06-03 02:04:25 ERROR juju.apiserver debuglog.go:226 Could not deduce name from tag "-machine-1": "-machine-1" is not a valid tag
2015/06/03 02:04:25 http: panic serving 27.33.46.253:51343: runtime error: invalid memory address or nil pointer dereference
goroutine 945 [running]:
net/http.func<C2><B7>011()
        /home/ian/.gvm/gos/go1.4/src/net/http/server.go:1130 +0xbb
github.com/juju/juju/apiserver.parseLogLine(0xc20812d440, 0xb4, 0x10b4)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:228 +0x43d
github.com/juju/juju/apiserver.(*logStream).filterLine(0xc20812d380, 0xc208530f4c, 0xb4, 0x10b4, 0x0)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:286 +0x54
github.com/juju/juju/apiserver.*logStream.(github.com/juju/juju/apiserver.filterLine)<C2><B7>fm(0xc208530f4c, 0xb4, 0x10b4, 0x2d6a249)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:262 +0x45
github.com/juju/utils/tailer.SeekLastLines(0x7fc4e9681ca0, 0xc20874c7f0, 0x3e8, 0xc208479790, 0x0, 0x0)
        /home/ian/juju/go/src/github.com/juju/utils/tailer/tailer.go:190 +0x691
github.com/juju/juju/apiserver.(*logStream).positionLogFile(0xc20812d380, 0x7fc4e9681ca0, 0xc20874c7f0, 0x0, 0x0)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:262 +0xa2
github.com/juju/juju/apiserver.func<C2><B7>011(0xc2082439e0)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:87 +0x7fc
golang.org/x/net/websocket.Server.serveWebSocket(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /home/ian/juju/go/src/golang.org/x/net/websocket/server.go:90 +0x292
golang.org/x/net/websocket.Server.ServeHTTP(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /home/ian/juju/go/src/golang.org/x/net/websocket/server.go:70 +0x5a
github.com/juju/juju/apiserver.(*debugLogHandler).ServeHTTP(0xc2080a7000, 0x7fc4e96654f8, 0xc208705720, 0xc20874fba0)
        /home/ian/juju/go/src/github.com/juju/juju/apiserver/debuglog.go:114 +0x139
github.com/bmizerany/pat.(*PatternServeMux).ServeHTTP(0xc208036248, 0x7fc4e96654f8, 0xc208705720, 0xc20874fba0)
        /home/ian/juju/go/src/github.com/bmizerany/pat/mux.go:109 +0x21c
net/http.serverHandler.ServeHTTP(0xc20813f560, 0x7fc4e96654f8, 0xc208705720, 0xc20874fba0)
        /home/ian/.gvm/gos/go1.4/src/net/http/server.go:1703 +0x19a
net/http.(*conn).serve(0xc208610c80)
        /home/ian/.gvm/gos/go1.4/src/net/http/server.go:1204 +0xb57
created by net/http.(*Server).Serve
        /home/ian/.gvm/gos/go1.4/src/net/http/server.go:1751 +0x35e