vuejs#3566 | fix type issue

Author: izabela-grzeskowiak-allegro

Diff for: types/router.d.ts

@@ -200,7 +200,7 @@ export interface Route {
   path: string
   name?: string | null
   hash: string
-  query: Dictionary<string | (string | null)[]>
+  query: Dictionary<string | null | (string | null)[]>
   params: Dictionary<string>
   fullPath: string
   matched: RouteRecord[]