Use "visibility: hidden" instead of "display:none" to hide the dropdown menu

[LinAlSara]

Problem I want to open the dropdown menu by default downwards and only if the dropdown menu list will be at the end of the page (it will be cut & user has to scroll to see the dropdown list) then open it upwards. The problem with the current implementation is that 'display: none' is used which means the dropdown menu does not appear in the dom & therefore I can not detect if the dropdown menu list will be at the end of the page. So I suggest using visibility: hidden instead of 'display: none'.

[coveralls]

Coverage remained the same at 95.652% when pulling bc1ce75efc5b406be9e862ddf5037224b1ce7402 on LinAlSara:enhancement/UseVisibilityHiddenInsteadOfDisplayNone into 2203ee05416fe0ac2585395f9094e5c21b8ebcbc on trendmicro-frontend:master.