[TYPO3-mvc] make use of the new propertyMapper feature in 4.7

[Domi]

Hello,

I just try the new propertyMapper for my current extension. I am not 
sure why I get immediatly exceptions, googled it but still not sure how 
to solve it:

controller:
  $countries = $this->countryRepository->findAllWithoutPid();
  $this->view->assign('countries', $countries);

fluid template:
<f:form.select id="countries" property="countries" 
options="{countries}" optionValueField="uid"			 
optionLabelField="name" multiple="TRUE" class="{class}"/>

If I submit my form I get following error:

Exception while property mapping at property path "travelTypes":Object 
with identity "1" not found

How is this suppose to work? Or is the rewritten property mapper for now 
not mature enough to use?


Thanks for any hint

Dominic