Chore: upgrade to Typescript 3.9.3 (#25154)

* upgrade to typescript 3.9.3

* Fix errors that surfaced with update

* Null check fixs

* FIx null checks

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

public/app/features/folders/state/navModel.ts

@@ -42,6 +42,8 @@ export function getLoadingNav(tabIndex: number): NavModel {
     title: 'Loading',
     url: 'url',
     canSave: false,
+    canEdit: false,
+    canAdmin: false,
     version: 0,
   });
 

public/app/features/folders/state/reducers.test.ts

@@ -9,6 +9,8 @@ function getTestFolder(): FolderDTO {
     uid: 'asd',
     url: 'url',
     canSave: true,
+    canEdit: true,
+    canAdmin: true,
     version: 0,
   };
 }