Updated to angular 11

Now compiling with strict mode in typescript
Need to error checking now

bookie/src/app/modifiers/modifier.service.ts

@@ -17,7 +17,7 @@ const serviceName = 'ModifierService';
 export class ModifierService {
   constructor(private http: HttpClient, private log: ErrorLoggerService) {}
 
-  get(id: string): Observable<Modifier> {
+  get(id: string | null): Observable<Modifier> {
     const getUrl: string = id === null ? url : `${url}/${id}`;
     return <Observable<Modifier>>(
       this.http