[AAE-622] No implicit returns (#5157)

* enable noImplicitReturns rule

* type fixes

* fix return types

* fix return value

* fix tests

* fix visibility service

* update tests

* add missing types

* fix test

lib/core/viewer/services/view-util.service.ts

@@ -126,6 +126,8 @@ export class ViewUtilService {
                 return await this.waitRendition(nodeId, renditionId, retries);
             }
         }
+
+        return Promise.resolve(null);
     }
 
     getViewerTypeByMimeType(mimeType: string): string {