change handlermanager to use Map to prevent garbage

src/ViewModel/Pages/boardViewModel.ts

@@ -278,7 +278,7 @@ export default class BoardViewModel extends TaskContainingPageViewModel {
         });
 
         // handlers
-        boardsAndTasksModel.taskHandlerManager.addHandler(
+        boardsAndTasksModel.taskHandlerManager.setHandler(this.boardInfo.fileId,
             (taskFileContent: TaskFileContent) => {
                 if (taskFileContent.boardId != this.boardInfo.fileId) return;
                 this.showTask(taskFileContent);

src/ViewModel/Pages/calendarPageViewModel.ts

@@ -200,7 +200,7 @@ export default class CalendarPageViewModel extends TaskContainingPageViewModel {
         });
 
         // handlers
-        boardsAndTasksModel.taskHandlerManager.addHandler(
+        boardsAndTasksModel.taskHandlerManager.setHandler("calendar" + this.chatViewModel.chatModel.id,
             (taskFileContent: TaskFileContent) => {
                 this.showTask(taskFileContent);
             },

src/ViewModel/Pages/taskPageViewModel.ts

@@ -175,7 +175,7 @@ export default class TaskPageViewModel extends ContextHost<string> {
         this.selectedBoardId.subscribeSilent(this.updateContexts);
 
         // handlers
-        boardsAndTasksModel.boardHandlerManager.addHandler(
+        boardsAndTasksModel.boardHandlerManager.setHandler("task-page" + this.chatViewModel.chatModel.id,
             (boardInfoFileContent: BoardInfoFileContent) => {
                 this.showBoardInList(boardInfoFileContent);
                 this.updateBoardIndices();