cairo-util: Fix geometry for frames with buttons but without title

cairo-util: Fix geometry for frames with buttons but without title

There exist frames which have buttons without title such as a simple
X application piped through xwayland which doesn't specify a title.
We draw the title bar with buttons, but hide it under the window
because geometry thinks a window needs titlebar only if it has title.

This patch change the condition, making it titlebar is needed if a
frame has title or has button(s), which makes more sense.

Signed-off-by: Boyan Ding <stu_dby@126.com>