delay hiding previews when creating contextmenu

• there are cases that hiding previews too early

can create crashes under wayland. Such a case is
when the user uses the touchpad to emulate a right-click
event to create a context menu for specific task

BUG: 397635
FIXED-IN: 0.8.1
(cherry picked from commit b4dd016ed0d861e9c1676cbd6edb425edbe6c966)