Tweaked the isXMLDoc iframe test case to test the document, not the b…

…ody element (which doesn't exist in IE). Also made the isXMLDoc code handle cases where elem is null, undefined, etc.

src/core.js

@@ -316,7 +316,7 @@ jQuery.extend({
 	isXMLDoc: function( elem ) {
 		// documentElement is verified for cases where it doesn't yet exist
 		// (such as loading iframes in IE - #4833)
-		return ((elem.ownerDocument || elem).documentElement || 0).nodeName !== "HTML";
+		return ((elem ? elem.ownerDocument || elem : 0).documentElement || 0).nodeName !== "HTML";
 	},
 
 	// Evalulates a script in a global context

test/unit/core.js

@@ -280,10 +280,10 @@ test("isXMLDoc - HTML", function() {
 	document.body.appendChild( iframe );
 
 	try {
-		var body = jQuery(iframe).contents().find("body")[0];
-		ok( !jQuery.isXMLDoc( body ), "Iframe body element" );
+		var body = jQuery(iframe).contents()[0];
+		ok( jQuery.isXMLDoc( body ), "Iframe body element" );
 	} catch(e){
-		ok( false, "Iframe body element" );
+		ok( false, "Iframe body element exception" );
 	}
 
 	document.body.removeChild( iframe );