Frontend_V2: Fix the JS error when loading all challenges on the chal…

…lenge page (#3449)

* remove js errors on challenge list apge

* fix js error

* fix windowscroll error

* add page scroll event

Co-authored-by: Rishabh Jain <rishabhjain2018@gmail.com>

frontend_v2/src/app/components/publiclists/challengelist/challengelist.component.html

@@ -3,7 +3,7 @@
   <div *ngIf="routerPublic.url === allChallengesRoutePathCommon" [@.disabled]="true">
     <h4 class="fw-light">All challenges</h4>
     <mat-tab-group>
-      <mat-tab label="Ongoing ({{ ongoingChallenges.length }})">
+      <mat-tab label="Ongoing ({{ ongoingChallenges.length }})" id="ongoing-challenges">
         <div *ngIf="ongoingChallenges.length === 0" class="none fw-light fs-16">No challenges found.</div>
         <div class="row pd-lr-20">
           <div class="col s12 m4 l3" *ngFor="let challenge of ongoingChallenges">

frontend_v2/src/app/components/publiclists/challengelist/challengelist.component.ts

@@ -38,7 +38,7 @@ export class ChallengelistComponent implements OnInit {
   /**
    * Ongoing challenges list
    */
-  ongoingChallenges: any;
+  ongoingChallenges = [];
 
   /**
    * Past challeges list
@@ -90,7 +90,7 @@ export class ChallengelistComponent implements OnInit {
   /**
    * List of filtered ongoing challenges
    */
-  filteredOngoingChallenges: any;
+  filteredOngoingChallenges = [];
 
   /**
    * List of filtered upcoming challenges