Fix json output

[feloy]

Running doa analyze with the option --o json pacnics:

./bin/doa analyze --f Dockerfile --o json
panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
github.com/redhat-developer/docker-openshift-analyzer/pkg/cli.doAnalyze(0xc0004f8900?, {0xc00070b5c0, 0x0, 0x4?})
	/home/phmartin/Documents/gits/podman-desktop-image-checker-openshift-ext/pkg/cli/analyze.go:45 +0x335
github.com/spf13/cobra.(*Command).execute(0xc0004f8900, {0xc00070b580, 0x4, 0x4})
	/home/phmartin/go/pkg/mod/github.com/spf13/[email protected]/command.go:920 +0x847
github.com/spf13/cobra.(*Command).ExecuteC(0xc0004f8600)
	/home/phmartin/go/pkg/mod/github.com/spf13/[email protected]/command.go:1044 +0x3bd
github.com/spf13/cobra.(*Command).Execute(...)
	/home/phmartin/go/pkg/mod/github.com/spf13/[email protected]/command.go:968
main.main()
	/home/phmartin/Documents/gits/podman-desktop-image-checker-openshift-ext/main.go:36 +0x14f

[jeffmaury]

LGTM