Back out one of the changes from the previous commit that wasn't necessary to...

Back out one of the changes from the previous commit that wasn't necessary to fix the bug and might not be desired.

src/core.js

@@ -553,7 +553,7 @@ jQuery.extend = jQuery.fn.extend = function() {
 					target[ name ] = jQuery.extend( target[ name ], options[ name ] );
 
 				// Don't bring in undefined values
-				else if ( options[ name ] !== undefined )
+				else if ( options[ name ] != undefined )
 					target[ name ] = options[ name ];
 
 			}

test/unit/core.js

@@ -874,7 +874,7 @@ test("$.extend(Object, Object)", function() {
 	ok( typeof ret.foo != "string", "Check to make sure values equal with coersion (but not actually equal) overwrite correctly" );
 
 	var ret = jQuery.extend(true, { foo:"bar" }, { foo:null } );
-	equals( ret.foo, null, "Check to make sure values equal with coersion (but not actually equal) overwrite correctly" );
+	ok( typeof ret.foo !== 'undefined', "Make sure a null value doesn't crash with deep extend, for #1908" );
 
 	var defaults = { xnumber1: 5, xnumber2: 7, xstring1: "peter", xstring2: "pan" },
 		defaultsCopy = { xnumber1: 5, xnumber2: 7, xstring1: "peter", xstring2: "pan" },