When editing a value in grid, if you write only numeric digits then the value is considered to be float regardless of column type, so, if you put '1' in a varchar field, the field is updated with "1.000000" value. So it is impossible to edit a varchar field if you intend to write only numeric chars. Edit integer fields it is impossible at all, since it raises an error "Invalid Integer Numeric Value".
The error is present from 0.9.3.8 version, and still present with 0.9.3.9. In the screenshot, I'm trying to write "1048" in "COD" colum, defined as Varchar(4).