ui-refs: remove useless null check

There is no way that "tag" can be null here.

Coverity-id: 13950
Signed-off-by: John Keeping <john@keeping.me.uk>

ui-refs.c

@@ -135,7 +135,7 @@ static int print_tag(struct refinfo *ref)
 		tag = (struct tag *)obj;
 		obj = tag->tagged;
 		info = ref->tag;
-		if (!tag || !info)
+		if (!info)
 			return 1;
 	}