bugfix for using multiple dialogs parallel

[ray007]

In jquery.mobile.simpledialog2.js, line 338 (function 'destroy'): instead of

$.mobile.sdCurrentDialog.sdIntContent.find('select').each(function() {

you probably meant to write

self.sdIntContent.find('select').each(function() {

otherwise trying to close the 2nd dialog brings an exception and leaves the screen.