Fix toggling storage cleanup

Setting item to null, still keeps an entry in localStorage
This also breaks the old implementation in the case of rollback
which happened today.

This patch adds some safe guards to make sure any existing broken
states are fixed, any the entry is removed going forward.

Bug: T272638
Change-Id: Ib7c0a45fcf8645a900288a26d172781612fa1606

src/mobile.startup/Toggler.js

@@ -42,6 +42,10 @@ function Toggler( options ) {
  */
 function getExpandedSections( page ) {
 	var expandedSections = JSON.parse( mw.storage.session.get( 'expandedSections' ) || '{}' );
+	// Can be removed 1 week after Ib7c0a45fcf8645a900288a26d172781612fa1606 is deployed
+	if ( expandedSections === 'null' ) {
+		expandedSections = {};
+	}
 	expandedSections[page.title] = expandedSections[page.title] || {};
 	return expandedSections;
 }
@@ -55,7 +59,10 @@ function saveExpandedSections( expandedSections ) {
 		mw.storage.session.set(
 			'expandedSections', JSON.stringify( mw.storage.get( 'expandedSections' ) )
 		);
-		mw.storage.set( 'expandedSections', null );
+		// Clean up any old storage.
+		// The following line can be removed 1 week after
+		// Ib7c0a45fcf8645a900288a26d172781612fa1606 is deployed
+		mw.storage.remove( 'expandedSections' );
 	}
 	mw.storage.session.set(
 		'expandedSections', JSON.stringify( expandedSections )