Non-existing values evaluate to some random value in facelets custom component

Question

I have written a custom facelet component which looks like this:

<ice:inputText
            styleClass="datepicker"
            required="#{required}"
            id="#{cid}"
            disabled="#{disabled }"
            validator="notnull"
            value="#{value}"
            rendered="#{empty binding }">

        </ice:inputText>                    
        <ice:inputText
            styleClass="datepicker"
            required="#{required}"
            id="#{cid}"
            disabled="#{disabled }"
            validator="notnull"
            value="#{value}"
            binding="#{binding}"
            rendered="#{not empty binding}">


        </ice:inputText>

As you can see there are two options, binding is set or binding is not set. The problem now is that if I use the control by using a custom tag (ft:dateInput) and do NOT set a binding value this value is there non-the-less.

<ft:dateInput cid="myId" 
                required="true"                 
                value="#{mybean.user.demoDate}"
                disabled="#{mybean.confirmMode }"
                label="Completed Demo Date:" />

I added a debug output #{binding} and saw that it evaluates to the last com.icesoft.faces.component.ext.HtmlInputText object in the tag. Very strange!

So my question: is this behaviour normal, is it a bug? Why the single tags are sharing values? Thanks.