The bug report is located at https://gna.org/bugs/?func=detailitem&item_id=5660.
To fix the bug, a function in the base class of the specific functions has been added called
'self.has_error()'. This function checks the diffusion tensor data structures and the residue
specific data structures for error objects by looping over all objects 'object_name' and seeing if
there is a corresponding object called 'object_name' + '_err'.
The model-free results writing function now checks the 'self.has_error()' result and if successful,
then the error section is executed. The simulation section has also been modified to improve
flexibility.
