activated typescript strict mode

src/app/modules/guest/guest.component.ts

@@ -2,8 +2,10 @@ import {Component, OnInit} from '@angular/core';
 import {SongService} from '../songs/services/song.service';
 import {GlobalSettingsService} from '../../services/global-settings.service';
 import {Observable} from 'rxjs';
-import {map, switchMap} from 'rxjs/operators';
+import {filter, map, switchMap} from 'rxjs/operators';
 import {ShowSongService} from '../shows/services/show-song.service';
+import {GlobalSettings} from '../../services/global-settings';
+import {Song} from '../songs/services/song';
 
 @Component({
   selector: 'app-guest',
@@ -11,15 +13,31 @@ import {ShowSongService} from '../shows/services/show-song.service';
   styleUrls: ['./guest.component.less'],
 })
 export class GuestComponent implements OnInit {
-  public songs$: Observable<Observable<string>[]>;
+  public songs$: Observable<Observable<string>[]> | null = null;
 
-  public constructor(private songService: SongService, private globalSettingsService: GlobalSettingsService, private showSongService: ShowSongService) {}
+  public constructor(
+    private songService: SongService,
+    private globalSettingsService: GlobalSettingsService,
+    private showSongService: ShowSongService
+  ) {}
 
   public ngOnInit(): void {
     this.songs$ = this.globalSettingsService.get$.pipe(
+      filter(_ => !!_),
+      map(_ => _ as GlobalSettings),
       map(_ => _.currentShow),
       switchMap(_ => this.showSongService.list$(_)),
-      map(_ => _.sort((x, y) => x.order - y.order).map(showSong => this.songService.read$(showSong.songId).pipe(map(song => song.text))))
+      filter(_ => !!_),
+      map(_ => _),
+      map(_ =>
+        _.sort((x, y) => x.order - y.order).map(showSong =>
+          this.songService.read$(showSong.songId).pipe(
+            filter(_ => !!_),
+            map(_ => _ as Song),
+            map(song => song.text)
+          )
+        )
+      )
     );
   }
 }