Ah, mayby just use identifier? That would also resolve a problem of lack of both title and description. To sum up: if title is empty, use identifier (Q<some number>) and if description is empty, omit it. Is that acceptable?
Let us try to avoid displaying the identifier. Instead, if there is no label and only a description treat it the same way as if there is no label and no description (that's an unusual situation anyway). In that case, probably nothing should be shown.