Prevents the menu from closing when the user clicks the input field

[benjamin-albert]

This is a fix for #22.
The culprit was my quick fix for #19

// If there is an open menu close it first.
if (_openedInstance) {
    _openedInstance.Close(event);
}

It was placed right before this:

if (!this._visible) {
    //open the menu
}

So when the user clicks the input field the opened menu will first be closed and then !this._visible will evaluate to true and the menu will be reopened.

I fixed this the by moving the close opened menu code (and some other code) into the
if (!this._visible).