Fix nogroup regression, where nogroup became an actual group - the

symantics between cwm groups and ewmh got in the way.  Ensure a client
that wants to be in nogroup stays in nogroup (thus stays in view), even
when (re)reading NET_WM_DESKTOP.  Paritially reverts patchset 644
(2014-02-07 13:09 PST) which deals with a NULL cc->group.  All to be
revisited when NET_WM_STATE_STICKY hits cwm.

Reported by many; testing and ok phessler.

mousefunc.c

@@ -202,7 +202,8 @@ mousefunc_menu_unhide(struct client_ctx *cc, union arg *arg)
 			if (wname == NULL)
 				continue;
 
-			menuq_add(&menuq, cc, "(%d) %s", cc->group->num, wname);
+			menuq_add(&menuq, cc, "(%d) %s",
+			    cc->group ? cc->group->num : 0, wname);
 		}
 
 	if (TAILQ_EMPTY(&menuq))