switch filter to Subject from BehaviorSubject

src/app/services/filter.service.ts

@@ -1,29 +1,26 @@
 import { Injectable } from '@angular/core';
 import { StType } from '../type';
-import { BehaviorSubject } from 'rxjs';
-
-@Injectable({
-  providedIn: 'root'
-})
+import { Subject } from 'rxjs';
 
 export interface FilterInput {
   type: StType;
   text: string
 }
 
+@Injectable({
+  providedIn: 'root'
+})
 export class FilterService {
   previousInputs = new Map<StType, string>(
     [
       [StType.Folder, ""],
       [StType.Device, ""],
     ]
-
   )
 
   constructor() { }
 
-  private filterChangeSource = new BehaviorSubject<FilterInput>({ type: StType.Folder, text: "" });
-
+  private filterChangeSource = new Subject<FilterInput>();
   filterChanged$ = this.filterChangeSource.asObservable();
 
   changeFilter(input: FilterInput) {