Updated to angular 11

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

bookie/src/app/beer-sale-report/beer-sale-report.service.ts

@@ -16,7 +16,7 @@ const serviceName = 'BeerSaleReportService';
 export class BeerSaleReportService {
   constructor(private http: HttpClient, private log: ErrorLoggerService) {}
 
-  get(startDate: string, finishDate): Observable<BeerSaleReport> {
+  get(startDate: string | null, finishDate: string | null): Observable<BeerSaleReport> {
     const options = { params: new HttpParams() };
     if (startDate !== null) {
       options.params = options.params.set('s', startDate);