TreeTable required selection validation problem

[mertsincan]

Reported by Pro User;
I can submit a p:treeTable which is selectable and required with an empty selection.
Examplecode - modified from Showcase-Example
<h:panelGrid columns="1" cellpadding="5" id="myPanelGrid"> <p:message for="testTreeTable" /> <p:treeTable id="testTreeTable" value="#{ttSelectionView.root1}" var="document" required="true" selectionMode="single" selection="#{ttSelectionView.selectedNode}"> <p:column headerText="Name"> <h:outputText value="#{document.name}" /> </p:column> <p:column headerText="Size"> <h:outputText value="#{document.size}" /> </p:column> <p:column headerText="Type"> <h:outputText value="#{document.type}" /> </p:column> </p:treeTable> <p:separator/> <p:outputLabel value="selectedNode: #{ttSelectionView.selectedNode}"/> </h:panelGrid> <p:commandButton update="myPanelGrid" process="myPanelGrid" value="Submit" />

Steps to reproduce:

1. Select an entry and press submit
2. deselect the entry and press submit
   => now we see the empty selection is stored in the backend
3. press submit again
   => Now we see the Required-Error-Message