falcon-agent --check panic

[taomaree]

./falcon-agent -v
5.1.2

./falcon-agent -c cfg.json run as well,
./falcon-agent -c cfg.json --check panic
cfg.json with or without "mountPoint": [""] , panic still exists.

./falcon-agent -c cfg.json --check

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x48 pc=0x73a9ae]

goroutine 1 [running]:
github.com/open-falcon/falcon-plus/modules/agent/funcs.DeviceMetrics(0x7f64a0, 0xc4200fbda0, 0xc4200fbca0)
	/root/go/src/github.com/open-falcon/falcon-plus/modules/agent/funcs/dfstat.go:21 +0xfe
github.com/open-falcon/falcon-plus/modules/agent/funcs.CheckCollector()
	/root/go/src/github.com/open-falcon/falcon-plus/modules/agent/funcs/checker.go:21 +0x1f5
main.main()
	/root/go/src/github.com/open-falcon/falcon-plus/modules/agent/main.go:27 +0x1d4