Fixes #8277. Sets data to undefined rather than null when it is not provided...

Fixes #8277. Sets data to undefined rather than null when it is not provided in ajax helpers so that it won't revent data set in ajaxSettings from being used. Unit test added.

src/ajax.js

@@ -164,7 +164,7 @@ jQuery.fn.extend({
 			if ( jQuery.isFunction( params ) ) {
 				// We assume that it's the callback
 				callback = params;
-				params = null;
+				params = undefined;
 
 			// Otherwise, build a param string
 			} else if ( typeof params === "object" ) {
@@ -256,7 +256,7 @@ jQuery.each( [ "get", "post" ], function( i, method ) {
 		if ( jQuery.isFunction( data ) ) {
 			type = type || callback;
 			callback = data;
-			data = null;
+			data = undefined;
 		}
 
 		return jQuery.ajax({
@@ -272,7 +272,7 @@ jQuery.each( [ "get", "post" ], function( i, method ) {
 jQuery.extend({
 
 	getScript: function( url, callback ) {
-		return jQuery.get( url, null, callback, "script" );
+		return jQuery.get( url, undefined, callback, "script" );
 	},
 
 	getJSON: function( url, data, callback ) {

test/unit/ajax.js

@@ -1196,6 +1196,21 @@ test("load(String, String, Function)", function() {
 	});
 });
 
+test("jQuery.get(String, Function) - data in ajaxSettings (#8277)", function() {
+	expect(1);
+	stop();
+	jQuery.ajaxSetup({
+		data: "helloworld"
+	});
+	jQuery.get(url('data/echoQuery.php'), function(data) {
+		ok( /helloworld$/.test( data ), 'Data from ajaxSettings was used');
+		jQuery.ajaxSetup({
+			data: null
+		});
+		start();
+	});
+});
+
 test("jQuery.get(String, Hash, Function) - parse xml and use text() on nodes", function() {
 	expect(2);
 	stop();