[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/components/txtViewer.component.ts

@@ -55,6 +55,8 @@ export class TxtViewerComponent implements OnChanges {
         if (!this.urlFile && !this.blobFile) {
             throw new Error('Attribute urlFile or blobFile is required');
         }
+
+        return Promise.resolve();
     }
 
     private getUrlContent(url: string): Promise<any> {