Added a fix to prevent the completion callback from firing multiple t…

…imes in Firefox on OSX (fixed bug #1406).

src/ajax/ajax.js

@@ -622,7 +622,7 @@ jQuery.extend({
 		// Wait for a response to come back
 		var onreadystatechange = function(isTimeout){
 			// The transfer is complete and the data is available, or the request timed out
-			if ( xml && (xml.readyState == 4 || isTimeout == "timeout") ) {
+			if ( !requestDone && xml && (xml.readyState == 4 || isTimeout == "timeout") ) {
 				requestDone = true;
 
 				// clear poll interval