Check key error when deleting rendernode
Check key error when deleting rendernode

Fix an error when a request is sent to delete a rendernode.
Still need to fix the fact that the node deletion is called twice (see rendernode change listener)

smaragden/OpenRenderManagement,smaragden/OpenRenderManagement,smaragden/OpenRenderManagement,mikrosimage/OpenRenderManagement,mikrosimage/OpenRenderManagement,mikrosimage/OpenRenderManagement