The EchoTrack plugin crashes in QmitkUSNavigationStepCombinedModality::OnCombinedModalityCreationExit() when pressing the "Create Combined Modality" button. Currently

1. The wrong name of the DataNode used for view initialization is provided ("US Viewing Stream")
2. There is no check for validity for the DataNode

Crash can be reproduced with the following build configuration: Windows 7, 32 bit