fix: terminate timer tasks when ran

src/main/java/fr/insa/clavardator/chat/ChatHistory.java

@@ -59,6 +59,7 @@ public class ChatHistory {
 			@Override
 			public void run() {
 				Platform.runLater(() -> notifyHistoryLoaded());
+				t.cancel();
 			}
 		}, 1000);
 	}

src/main/java/fr/insa/clavardator/ui/MainController.java

@@ -86,6 +86,7 @@ public class MainController implements Initializable {
 			@Override
 			public void run() {
 				Platform.runLater(() -> CurrentUser.getInstance().setState(CurrentUser.State.VALID));
+				t.cancel();
 			}
 		}, 3000);
 

src/main/java/fr/insa/clavardator/ui/dialogs/EditUsernameDialogController.java

@@ -54,6 +54,7 @@ public class EditUsernameDialogController implements Initializable {
 			public void run() {
 //				onError();
 				onSuccess();
+				t.cancel();
 			}
 		}, 1000);
 	}