same issue as ZK-3501
1) caused again since zkmax 8.0.0 (timepicker styles)
2) also caused by modern themes from both combo and timepicker stylesheets
https://github.com/zkoss/zkThemeTemplate/blob/v8.6.0/src/archive/web/js/zul/inp/less/combo.less#L27
3) any other occurrence of sibling selectors ~/+ and :hover in the same resulting css style rule