Fixes issue when select box moves from display:none; to display:block;

When the select box starts off as display:none; $('select').emit('update') will measure out a near-zero width.  This causes issues when you have the select box display, and then call update.. It doesn't unset that width, so outerWidth gets that same near-zero size.  This unsets that width before measurement, which should result in more reliable measurements.