fix: avoid panic with plugin without description

[ldez]

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
github.com/golangci/golangci-lint/pkg/commands.formatDescription({0x0, 0x0})
        /tmp/custom-gcl2430187412/golangci-lint/pkg/commands/help.go:222 +0x125
github.com/golangci/golangci-lint/pkg/commands.printLinters({0xc0006251c0, 0x7, 0xc0006ad428?})
        /tmp/custom-gcl2430187412/golangci-lint/pkg/commands/help.go:187 +0x1d9
github.com/golangci/golangci-lint/pkg/commands.(*lintersCommand).execute(0xc000926f50, 0xc000743a90?, {0x0?, 0x0?, 0x0?})
        /tmp/custom-gcl2430187412/golangci-lint/pkg/commands/linters.go:102 +0x285
github.com/spf13/cobra.(*Command).execute(0xc000910308, {0x2a45c40, 0x0, 0x0})
        /home/ldez/sources/go/pkg/mod/github.com/spf13/[email protected]/command.go:985 +0xaaa
github.com/spf13/cobra.(*Command).ExecuteC(0xc000910008)
        /home/ldez/sources/go/pkg/mod/github.com/spf13/[email protected]/command.go:1117 +0x3ff
github.com/spf13/cobra.(*Command).Execute(...)
        /home/ldez/sources/go/pkg/mod/github.com/spf13/[email protected]/command.go:1041
github.com/golangci/golangci-lint/pkg/commands.(*rootCommand).Execute(0xc00090c750)
        /tmp/custom-gcl2430187412/golangci-lint/pkg/commands/root.go:83 +0x3d
github.com/golangci/golangci-lint/pkg/commands.Execute({{0x1e16388, 0x8}, {0x1e1e5f0, 0x12}, {0x1e0d768, 0x1}, {0x1e2c040, 0x27}})
        /tmp/custom-gcl2430187412/golangci-lint/pkg/commands/root.go:17 +0x5a
main.main()
        /tmp/custom-gcl2430187412/golangci-lint/cmd/golangci-lint/main.go:25 +0xc5