spice: fix coverity complains

Remove the unnecessary NULL check.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1463047028-123868-3-git-send-email-arei.gonglei@huawei.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

ui/spice-display.c

@@ -774,9 +774,7 @@ static void display_mouse_define(DisplayChangeListener *dcl,
     SimpleSpiceDisplay *ssd = container_of(dcl, SimpleSpiceDisplay, dcl);
 
     qemu_mutex_lock(&ssd->lock);
-    if (c) {
     cursor_get(c);
-    }
     cursor_put(ssd->cursor);
     ssd->cursor = c;
     ssd->hot_x = c->hot_x;