Description of problem:
After populating a decision table and then went back to alter an operator pertaining to an existing column, all the existing values in that column were deleted. We would expect the existing data to remain.

Version-Release number of selected component (if applicable):
6.2.0

How reproducible:
Always

Steps to Reproduce:
1. Create a Data Object and add some fields;
2. Create a Guided Decision Table;
3. Add some conditions using a field from the Data Object and add an operator (i.e. greather than);
4. Add some values to that column;
5. Edit that column and change the operator (i.e. less than);
6. Go back to the columns... all values for that column should be missing.

Actual results:
Values are missing after changing the operator.

Expected results:
The existing that should remain.

Additional info: