Tests: Handle jQuery git returning null for empty attributes

jQuery now returns `null` for empty attributes instead of `undefined`.

tests/unit/core/core.js

@@ -127,11 +127,11 @@ test( "outerHeight(true) - setter", function() {
 test( "uniqueId / removeUniqueId", function() {
 	expect( 3 );
 	var el = $( "img" ).eq( 0 );
-	strictEqual( el.attr( "id" ), undefined, "element has no initial id" );
+	equal( el.attr( "id" ), null, "element has no initial id" );
 	el.uniqueId();
 	ok( /ui-id-\d+$/.test( el.attr( "id" ) ), "element has generated id" );
 	el.removeUniqueId();
-	strictEqual( el.attr( "id" ), undefined, "unique id has been removed from element" );
+	equal( el.attr( "id" ), null, "unique id has been removed from element" );
 });
 
 })( jQuery );

tests/unit/dialog/dialog_core.js

@@ -78,7 +78,7 @@ test( "ARIA", function() {
 	element.remove();
 
 	element = $("<div><div aria-describedby='section2'><p id='section2'>descriotion</p></div></div>").dialog();
-	strictEqual( element.dialog( "widget" ).attr( "aria-describedby" ), undefined, "no aria-describedby added, as already present in markup" );
+	equal( element.dialog( "widget" ).attr( "aria-describedby" ), null, "no aria-describedby added, as already present in markup" );
 	element.remove();
 });
 

tests/unit/menu/menu_options.js

@@ -107,11 +107,11 @@ test( "{ role: null }", function( assert ) {
 		}),
 		items = element.find( "li" );
 	expect( 2 + 3 * items.length );
-	strictEqual( element.attr( "role" ), undefined );
+	equal( element.attr( "role" ), null );
 	ok( items.length > 0, "number of menu items" );
 	items.each(function( item ) {
 		assert.hasClasses( $( this ), "ui-menu-item" );
-		equal( $( this ).find( ".ui-menu-item-wrapper" ).attr( "role" ), undefined,
+		equal( $( this ).find( ".ui-menu-item-wrapper" ).attr( "role" ), null,
 			"menu item ("+ item + ") role" );
 		equal( $( this ).find( ".ui-menu-item-wrapper" ).attr( "tabindex" ), "-1",
 			"tabindex for menu item ("+ item + ")" );

tests/unit/progressbar/progressbar_core.js

@@ -55,7 +55,7 @@ test( "accessibility", function() {
 	element.progressbar( "option", "value", false );
 	equal( element.attr( "aria-valuemin" ), 0, "aria-valuemin" );
 	equal( element.attr( "aria-valuemax" ), 150, "aria-valuemax" );
-	strictEqual( element.attr( "aria-valuenow" ), undefined, "aria-valuenow" );
+	equal( element.attr( "aria-valuenow" ), null, "aria-valuenow" );
 });
 
 }( jQuery ) );

tests/unit/tooltip/tooltip_core.js

@@ -38,8 +38,7 @@ test( "accessibility", function() {
 	equal( element.attr( "aria-describedby" ), "fixture-span " + tooltipId,
 		"multiple describedby when open" );
 
-	// strictEqual to distinguish between .removeAttr( "title" ) and .attr( "title", "" )
-	strictEqual( element.attr( "title" ), undefined, "no title when open" );
+	equal( element.attr( "title" ), null, "no title when open" );
 	equal( liveRegion.children().length, 1 );
 	equal( liveRegion.children().last().html(), "..." );
 	element.tooltip( "close" );

tests/unit/tooltip/tooltip_methods.js

@@ -70,7 +70,7 @@ test( "enable/disable", function( assert ) {
 	assert.lacksClasses( element.tooltip( "widget" ), "ui-state-disabled" );
 	ok( !element.tooltip( "widget" ).attr( "aria-disabled" ), "element doesn't get aria-disabled" );
 	assert.lacksClasses( element.tooltip( "widget" ), "ui-tooltip-disabled" );
-	strictEqual( tooltip.attr( "title" ), undefined, "title removed on disable" );
+	equal( tooltip.attr( "title" ), null, "title removed on disable" );
 
 	element.tooltip( "open" );
 	equal( $( ".ui-tooltip" ).length, 0, "open does nothing when disabled" );