State is null in replacingStringFieldImp

[Constantine]

Hi.

I'm using TDA 2015.1.225.1. 

I've got a NullReferenceException in OpenAccessRuntime.DataObjects.PCStateMan.replacingStringFieldImp.

this.state is null in the code below:

internal string replacingStringFieldImp(PersistenceCapable pc, FieldMetaData fmd)
 {
  string str;
  try
  {
   string stringField = this.state.getStringField(fmd.stateFieldNo);
   this.setLoaded(fmd);
   str = stringField;
  }
  catch (Exception exception)
  {
   this.handleException(exception);
   return null;
  }
  return str;
 }

 

What can I do to fix the NullReferenceException? Why does this situation occur?