Redmine Computable Custom Field

The method ModelPatch#calculate_computable_field is rescued in case an exception will be raised.

This is only a workaround:

Since the method ModelPatch#calculate_computable_field is executed before_validation adding an error
won't take effect since errors are cleared before validation starts. The value 'unsupported_formula' won't be rendered since strings are casted to float or integers. The user will see a '0' or '0.00' instead.