showing log changes fails with custom data field that is not assigned to an option group

Steps to reproduce:

• create a alphanumeric custom data field and you do not use a select or radio list (just plain text field)
• enable logging
• change a record, including the custom data field you created
• view change log

You get:

Sorry. A non-recoverable error has occurred.
One of parameters (value: ) is not of the type Integer

Return to home page.

The problem seems to be that the logging code assumes that there's an option group id. I'm working on a commit that tests for this condition.