chore(volume): Add nil pointer checks and tests for outputResult func…

[Fyusel]

fixes: #574

[marceljk]

stackit-cli/internal/cmd/beta/volume/delete/delete.go

Lines 59 to 64 in 31084ad

	volumeLabel, err := iaasUtils.GetVolumeName(ctx, apiClient, model.ProjectId, model.VolumeId)
	if err != nil {
	p.Debug(print.ErrorLevel, "get volume name: %v", err)
	volumeLabel = model.VolumeId
	}

Could you add an additional check here if the volume name is empty? If it's empty, it should use the volumeId as label
This would solve this issue #574