Disable a button.

src/app/core/components/header/header.component.html

@@ -24,6 +24,7 @@
   <div class="right">
     <button class="icon stroked primary"
         (click)="enableSelectionMode()"
+        [disabled]="isNoAnyTaskList()"
         matTooltip="Activer la sélection des task-lists"
         matTooltipPosition="left">
       <mat-icon>checklist_rtl</mat-icon>

src/app/core/components/header/header.component.ts

@@ -53,4 +53,8 @@ export class HeaderComponent implements OnInit, OnDestroy {
   disableSelectionMode(): void {
     this._taskListService.disableSelectionMode();
   }
+
+  isNoAnyTaskList(): boolean {
+    return this._taskListService.isNoAnyTaskList();
+  }
 }

src/app/core/service/task-list.service.ts

@@ -207,4 +207,8 @@ export class TaskListService {
   get selectedTaskList(): TaskList {
     return this._store.value?.selectedTaskLists[0];
   }
+
+  isNoAnyTaskList(): boolean {
+    return !this.store?.taskLists?.length;
+  }
 }