jquery ajax: misc optimization for $.fn.load().

src/ajax.js

@@ -12,8 +12,6 @@ jQuery.fn.extend({
 			url = url.slice(0, off);
 		}
 
-		callback = callback || function(){};
-
 		// Default to a GET request
 		var type = "GET";
 
@@ -56,6 +54,7 @@ jQuery.fn.extend({
 						// If not, just inject the full result
 						res.responseText );
 
+				if( callback )
 					self.each( callback, [res.responseText, status, res] );
 			}
 		});