Make sure null/NaN values aren't set in .css(). Fixes #7116.

src/css.js

@@ -70,7 +70,7 @@ jQuery.extend({
 	style: function( elem, name, value, extra ) {
 		// Don't set styles on text and comment nodes
 		if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 || !elem.style ) {
-			return undefined;
+			return;
 		}
 
 		// Make sure that we're working with the right name
@@ -81,6 +81,11 @@ jQuery.extend({
 
 		// Check if we're setting a value
 		if ( value !== undefined ) {
+			// Make sure that NaN and null values aren't set. See: #7116
+			if ( typeof value === "number" && isNaN( value ) || value == null ) {
+				return;
+			}
+
 			// If a number was passed in, add 'px' to the (except for certain CSS properties)
 			if ( typeof value === "number" && !jQuery.cssNumber[ origName ] ) {
 				value += "px";

test/unit/css.js

 module("css");
 
 test("css(String|Hash)", function() {
-	expect(29);
+	expect(33);
 
 	equals( jQuery('#main').css("display"), 'none', 'Check for css property "display"');
 
@@ -61,6 +61,26 @@ test("css(String|Hash)", function() {
 	equals( prctval, checkval, "Verify fontSize % set." );
 
 	equals( typeof child.css("width"), "string", "Make sure that a string width is returned from css('width')." );
+
+	var old = child[0].style.height;
+
+	// Test NaN
+	child.css("height", parseFloat("zoo"));
+	equals( child[0].style.height, old, "Make sure height isn't changed on NaN." );
+
+	// Test null
+	child.css("height", null);
+	equals( child[0].style.height, old, "Make sure height isn't changed on null." );
+
+	old = child[0].style.fontSize;
+
+	// Test NaN
+	child.css("font-size", parseFloat("zoo"));
+	equals( child[0].style.fontSize, old, "Make sure font-size isn't changed on NaN." );
+
+	// Test null
+	child.css("font-size", null);
+	equals( child[0].style.fontSize, old, "Make sure font-size isn't changed on null." );
 });
 
 test("css(String, Object)", function() {