Save intermediate callstack model also when callstack instance is invalid (simplifies debugging)
Current behavior: If the relationship solver provides an invalid callstack model, the validation fails and raises an exception which leads to NOT saving the callstack model. This behavior is implemented in /edu.kit.ipd.descartes.solving/src/edu/kit/ipd/descartes/solving/DMLPredictionProcess.java
Change to: Save the intermediate callstack model regardless if it is invalid or not. This simplifies debugging.