fix(sidebar): fix case when category comes back as null

internal_packages/account-sidebar/lib/account-sidebar.cjsx

@@ -43,6 +43,7 @@ class AccountSidebar extends React.Component
 
   _itemComponents: (section) =>
     section.items?.map (item) =>
+      return unless item
       if item instanceof Category
         itemClass = AccountSidebarCategoryItem
       else if item.sidebarComponent

src/flux/stores/category-store.coffee

@@ -88,7 +88,7 @@ class CategoryStore extends NylasStore
     userCategories = _.reject _.values(@_categoryCache), (cat) =>
       cat.name in @StandardCategoryNames
     userCategories = _.sortBy(userCategories, 'displayName')
-    userCategories
+    return _.compact(userCategories)
 
   _onDBChanged: (change) ->
     categoryClass = @categoryClass()