Make sure prefilters have been called and transport has been selected before...

Make sure prefilters have been called and transport has been selected before sending any global event (in case the "global" option has been changed).

src/ajax.js

@@ -532,14 +532,14 @@ jQuery.extend({
 			s.data = jQuery.param( s.data , s.traditional );
 		}
 
+		// Get transport
+		transport = jQuery.ajax.prefilter( s ).transport( s );
+
 		// Watch for a new set of requests
 		if ( s.global && jQuery.active++ === 0 ) {
 			jQuery.event.trigger( "ajaxStart" );
 		}
 
-		// Get transport
-		transport = jQuery.ajax.prefilter( s ).transport( s );
-
 		// If no transport, we auto-abort
 		if ( ! transport ) {