setEmptyListTextWithAdvice() {
			var oRoleSelectionModel = this.getModel("selectedContexts");
			oRoleSelectionModel.setProperty("/noDataText",
				this.getRootControl().getController().oI18n.getText("NO_SELECTED_ROLES_WITH_ADVICE"));
			oRoleSelectionModel.refresh(true);
		}
Sets the text for an empty list with the advice to select at least one role