Cannot drop item from table to Calendar using Vaadin DnD

[Flaurite]

Environment

• Platform version: 7.2
• Client type: Web

Minimal reproducible example

1. Download attached project: demodnd.zip
2. Open Demo Screen and try to drag user and drop it to the Calendar

• Expected behavior Notification should be shown
• Actual behavior Gets an error from client-side:

Error: com.google.gwt.event.shared.UmbrellaException: Exception caught: (TypeError) : Cannot read property 'addEmphasisStyle_0_g$' of null
    at gjc_g$.java.lang.Throwable.createError [as createError_0_g$] (Throwable.java:120)
    at gjc_g$.java.lang.Throwable.initializeBackingError [as initializeBackingError_0_g$] (Throwable.java:112)
    at gjc_g$.java.lang.Throwable.Throwable (Throwable.java:73)
    at gjc_g$.java.lang.Exception.Exception (Exception.java:33)
    at gjc_g$.java.lang.RuntimeException.RuntimeException (RuntimeException.java:33)
    at gjc_g$.com.google.web.bindery.event.shared.UmbrellaException.UmbrellaException (UmbrellaException.java:65)
    at new com.google.gwt.event.shared.UmbrellaException.UmbrellaException (UmbrellaException.java:26)
    at Xhc_g$.com.google.gwt.event.shared.HandlerManager.fireEvent [as fireEvent_2_g$] (HandlerManager.java:129)
    at com.google.gwt.user.client.Event$NativePreviewEvent.fire (Event.java:87)
    at com.google.gwt.user.client.Event.fireNativePreviewEvent (Event.java:480)
    at com.google.gwt.user.client.DOM.previewEvent (DOM.java:1458)
    at com.google.gwt.user.client.impl.DOMImplStandard.dispatchCapturedMouseEvent (DOMImplStandard.java:345)
    at com.google.gwt.core.client.impl.Impl.apply (Impl.java:309)
    at com.google.gwt.core.client.impl.Impl.entry0 (Impl.java:361)
    at Impl.java:78

See com.vaadin.v7.client.ui.calendar.schedule.dd.CalendarWeekDropHandler class.