Make sure fragment caching is only happening on nodes in the main document. Fixes #5978.

src/manipulation.js

@@ -384,10 +384,15 @@ function cloneCopyEvent(orig, ret) {
 }
 
 function buildFragment( args, nodes, scripts ) {
-	var fragment, cacheable, cacheresults, doc;
+	var fragment, cacheable, cacheresults,
+		doc = (nodes && nodes[0] ? nodes[0].ownerDocument || nodes[0] : document);
+
+	// Only cache "small" (1/2 KB) strings that are associated with the main document
+	// Cloning options loses the selected state, so don't cache them
+	// Also, WebKit does not clone 'checked' attributes on cloneNode, so don't cache
+	if ( args.length === 1 && typeof args[0] === "string" && args[0].length < 512 && doc === document &&
+		args[0].indexOf("<option") < 0 && (jQuery.support.checkClone || !rchecked.test( args[0] )) ) {
 
-	// webkit does not clone 'checked' attribute of radio inputs on cloneNode, so don't cache if string has a checked
-	if ( args.length === 1 && typeof args[0] === "string" && args[0].length < 512 && args[0].indexOf("<option") < 0 && (jQuery.support.checkClone || !rchecked.test( args[0] )) ) {
 		cacheable = true;
 		cacheresults = jQuery.fragments[ args[0] ];
 		if ( cacheresults ) {
@@ -398,7 +403,6 @@ function buildFragment( args, nodes, scripts ) {
 	}
 
 	if ( !fragment ) {
-		doc = (nodes && nodes[0] ? nodes[0].ownerDocument || nodes[0] : document);
 		fragment = doc.createDocumentFragment();
 		jQuery.clean( args, doc, fragment, scripts );
 	}