ButtonBehavior: Fixed ImGuiButtonFlags_AllowOverlapMode to avoid temporarily activating widgets on click before they have been correctly double-hovered. (#319, #600)
// AllowOverlap mode (rarely used) requires previous frame HoveredId to be null or to match. This allows using patterns where a later submitted widget overlaps a previous one.
// AllowOverlap mode (rarely used) requires previous frame HoveredId to be null or to match. This allows using patterns where a later submitted widget overlaps a previous one.