PrimeFaces: Caused by: java.lang.IllegalStateException: CDATA tags may not nest

Caused by: java.lang.IllegalStateException: CDATA tags may not nest

in PrimeFaces.
This could be due to an inexisting reference value:
<p:confirmDialog id="confirmDialogExternal"
message=”#{messages[‘Remove-Question’]}”
header=”#{messages[‘Remove-Header’]}” severity=”alert”
widgetVar=”confirmDialogExternal”>
<p:commandButton id="confirm3" value="#{messages['Remove']}"
actionListener=”#{feedbackController.deleteObjective}”
oncomplete=”confirmDialogExternal.hide()” update=”activitiesExternal” />
<p:commandButton id="decline3" value="#{messages['Cancel']}"
onclick=”confirmDialogExternal.hide()” type=”button” />

If a control with ID activitiesExternal does not exist, then the error will happen.