Data: Work around IE11 bug with onpageshow attribute

Fixes #14894
(cherry picked from commit b8133e28)

Conflicts:
	src/data.js
	test/unit/data.js

src/data.js

@@ -287,12 +287,15 @@ jQuery.fn.extend({
 				if ( elem.nodeType === 1 && !jQuery._data( elem, "parsedAttrs" ) ) {
 					i = attrs.length;
 					while ( i-- ) {
-						name = attrs[i].name;
 
-						if ( name.indexOf("data-") === 0 ) {
-							name = jQuery.camelCase( name.slice(5) );
-
-							dataAttr( elem, name, data[ name ] );
+						// Support: IE11+
+						// The attrs elements can be null (#14894)
+						if ( attrs[ i ] ) {
+							name = attrs[ i ].name;
+							if ( name.indexOf( "data-" ) === 0 ) {
+								name = jQuery.camelCase( name.slice(5) );
+								dataAttr( elem, name, data[ name ] );
+							}
 						}
 					}
 					jQuery._data( elem, "parsedAttrs", true );

test/data/data/dataAttrs.html

+<!DOCTYPE html>
+<html>
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+	<title>IE11 onpageshow strangeness (#14894)</title>
+	<script src="../../jquery.js"></script>
+	<script>
+		$(function(){
+			window.parent.iframeCallback( $( "body" ).data().result );
+		});
+	</script>
+</head>
+<body x-what="test" data-result="ok" onload="x=1" onpageshow="x=1">
+    Test for #14894
+</body>
+</html>

test/unit/data.js

@@ -677,3 +677,9 @@ test( "JSON data- attributes can have newlines", function() {
 	equal( x.data("some").foo, "bar", "got a JSON data- attribute with spaces" );
 	x.remove();
 });
+
+testIframeWithCallback( "enumerate data attrs on body (#14894)", "data/dataAttrs.html", function( result ) {
+	expect(1);
+
+	equal(result, "ok", "enumeration of data- attrs on body" );
+});
\ No newline at end of file