I tried bothviewerCon:ViewerContainer = ViewerContainer.getInstace(); // inside init()
ViewerContainer.dispatchEvent(new AppEvent(AppEvent.WIDGET_RUN, viewerCon.getWidgetId("Selection") ) );
AND
ViewerContainer.dispatchEvent(new AppEvent(AppEvent.WIDGET_RUN, ViewerContainer.getInstance().getWidgetId("Selection") ) );
and I recieved the same error. Im probably making a stupid mistake somewhere.