netwm: Fix window type for broken clients

Bug: 15399

If a client specifies an invalid NET_WM_WINDOW_TYPE, fallback to normal
window type.

Signed-off-by: Olivier Fourdan <fourdan@xfce.org>

src/netwm.c

@@ -1346,7 +1346,7 @@ clientWindowType (Client * c)
     else
     {
         TRACE ("no \"net\" atom detected");
-        c->type = UNSET;
+        c->type = WINDOW_NORMAL;
         c->initial_layer = c->win_layer;
     }