[Bug] graph http api broken

[YouZhengChuan]

curl -vsq localhost:6071/history/

• Curl_http_done: called premature == 0
• Empty reply from server
• Connection #0 to host localhost left intact

$ cd ~/falcon-graph/
$ ./control tail

2017/05/12 18:08:51 server.go:2753: http: panic serving [::1]:59985: runtime error: index out of range
goroutine 20788 [running]:
net/http.(*conn).serve.func1(0xc4200a2c80)
	/usr/local/go/src/net/http/server.go:1721 +0xd0
panic(0x4474900, 0x4720b30)
	/usr/local/go/src/runtime/panic.go:489 +0x2cf
github.com/open-falcon/graph/http.configProcRoutes.func3(0x46fb0a0, 0xc4202582a0, 0xc42000aa00)
	/Users/youzhengchuan/go/src/github.com/open-falcon/graph/http/proc_http.go:30 +0x35c
net/http.HandlerFunc.ServeHTTP(0x450fe28, 0x46fb0a0, 0xc4202582a0, 0xc42000aa00)
	/usr/local/go/src/net/http/server.go:1942 +0x44
net/http.(*ServeMux).ServeHTTP(0x472f380, 0x46fb0a0, 0xc4202582a0, 0xc42000aa00)
	/usr/local/go/src/net/http/server.go:2238 +0x130
net/http.serverHandler.ServeHTTP(0xc4201ee000, 0x46fb0a0, 0xc4202582a0, 0xc42000aa00)
	/usr/local/go/src/net/http/server.go:2568 +0x92
net/http.(*conn).serve(0xc4200a2c80, 0x46fba20, 0xc420224680)
	/usr/local/go/src/net/http/server.go:1825 +0x612
created by net/http.(*Server).Serve
	/usr/local/go/src/net/http/server.go:2668 +0x2ce