simplified some initializers

force angular to detect style changes by introducing a 0 ms timeout in setPrintLockTo
remove unused references

src/main/webapp/app/layouts/main/main.component.ts

@@ -1,6 +1,5 @@
-import { Component, OnInit } from '@angular/core';
-import { ActivatedRouteSnapshot, NavigationEnd, Router } from '@angular/router';
-import { Observable } from 'rxjs';
+import { Component, OnInit} from '@angular/core';
+import { NavigationEnd, Router } from '@angular/router';
 
 import { JhiLanguageHelper } from '../../shared';
 import {PrintService} from "../../shared/util/print.service";
@@ -19,14 +18,13 @@ export class JhiMainComponent implements OnInit {
     ) {
     }
 
-    public isPrintLocked$: Observable<boolean>;
+    isPrintLocked$= this.printService.isPrintLocked$;
 
     ngOnInit() {
         this.router.events.subscribe((event) => {
             if (event instanceof NavigationEnd) {
                 this.jhiLanguageHelper.updateTitle();
             }
         });
-       this.isPrintLocked$ = this.printService.isPrintLocked$;
     }
 }

src/main/webapp/app/shared/subject/subject-pair-dialog.component.ts

@@ -1,4 +1,4 @@
-import { Component, Inject, OnDestroy, OnInit } from '@angular/core';
+import { Component, Inject, OnDestroy, OnInit} from '@angular/core';
 import { DatePipe, DOCUMENT } from '@angular/common';
 import { HttpResponse } from '@angular/common/http';
 import { ActivatedRoute, Params } from '@angular/router';

src/main/webapp/app/shared/util/print.service.ts

@@ -4,14 +4,11 @@ import { BehaviorSubject } from "rxjs";
 @Injectable({ providedIn: 'root' })
 export class PrintService {
 
-    public isPrintLocked$:  BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);
-
-    constructor(
-    ) {
-        this.isPrintLocked$.subscribe();
-    }
+    isPrintLocked$:  BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);
 
     setPrintLockTo(setTo: boolean) {
-        this.isPrintLocked$.next(setTo)
+        setTimeout(() => {
+            this.isPrintLocked$.next(setTo)
+        });
     }
 }