win: always update frame extents

Frame extents are only updated when the window has frame_opacity < 1.
However, window frames can have inherent transparency, and not having
the frame extents information for those windows breaks blur-background-frame.

Fixes #345

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/win.c

@@ -1001,7 +1001,6 @@ void win_mark_client(session_t *ps, struct managed_win *w, xcb_window_t client)
 	win_update_wintype(ps, w);
 
 	// Get frame widths. The window is in damaged area already.
-	if (ps->o.frame_opacity != 1)
 	win_update_frame_extents(ps, w, client);
 
 	// Get window group