Fix TinyMCE Firefox  Range.prototype error

The change is really simple but it's hard to spot in this changeset because tiny_mce.js and tiny_mce_jquery.js are minified.

basically this if statement:
if (!Range.prototype.getClientRects) {
is changed to:
if (!Range.prototype) {

since in Firefox Range.prototype is undefined.
Without this fix there are two potential failures:
1. Clicking on the style list will not bring up the style dropdown
2. Upon saving the object, after editing again the tinymce textarea is empty even though the html is present if you click the html button.