I woudn't say this is a bug, but it's unconvenient.
Try this:
- Create a table with some values.
- Transpose the table to remove type information.
- Append a Table Validator. Tell that validator to "Try to convert" a column.
- Delete some values in the original table so that the transposed column will contain only missing cells.
- Revalidate.
Observed Behaviour: The Validator will not fail, but he won't convert the column type either.
Expected Behaviour: The cells still contain missing values, but the column type is corrected.
Reason for expected behaviour: Some nodes like Java Snippets rely on columns having a particular type. The validators seem like a natural way to ensure type correctness.
Workaround: Manually make sure the types are correct (eg. with String Replacers, Math Formulas etc) like in the times before validators.