OZG-6499 first with filter instead of take

alfa-client/libs/postfach/src/lib/postfach-mail-form/postfach-mail.formservice.ts

@@ -32,7 +32,7 @@ import {
   UntypedFormGroup,
 } from '@angular/forms';
 import { ReplyOption } from 'libs/postfach-shared/src/lib/postfach.model';
-import { Observable, take } from 'rxjs';
+import { Observable, first } from 'rxjs';
 
 @Injectable()
 export class PostfachMailFormservice extends AbstractFormService {
@@ -63,11 +63,9 @@ export class PostfachMailFormservice extends AbstractFormService {
   public initMailBody(): void {
     this.postfachService
       .getSettings()
-      .pipe(take(1))
+      .pipe(first((settings) => !!settings.signatur))
       .subscribe((settings: PostfachSettings) => {
-        if (settings.signatur) {
         this.patchMailBodyWithSignaturAndNewline(settings.signatur);
-        }
       });
   }