UI Date picker opacity issue

UI Date picker opacity issue

I've isolated an issue that presents itself in Firefox where an inline style setting for opacity: 0 is being added when the date picker input is clicked.  It appears to be related to the application of any animation to the click event.  In the jquery-ui.js file, when I set the animation name to null in line 5866, the opacity value is not applied to the div named 'ui-datepicker-div'.  I've tested all available animations and they behave the same way.  Applicable to JQUI 1.11.2 using jQuery 1.11.2.