Building Info.plist was missing
input[type="file"].click() didn't work in Safari

Click couldn't be initiated with JavaScript in Safari if the input was
hidden with display: none. Using visibility: hidden or opacity: 0 solves
the problem.

Alternative solution would be to hide (opacity: 0) the input and slide it
(position: absolute; top: 0; left: 0; width: 100%; height: 100%) over the
button, which would work in all browsers, and wouldn't require JavaScript.