Bug: Importing an empty column in excel is not cosidered as empty

I have had great problems with this until i figured out what happened. When you import an excelsheet into the contacts module and it has a column in the sheet which does not contain data on every row it seems that during the import process Zoho CRM writes the empty cells to the mapped fields in Zoho and from then on those fields are considered not empty.

For instance i import 100 contacts of which there is column called 'starting date' in the excelsheet. Some contacts have a starting date and some don't. After importing them i used a custom view in the contacts module that uses the criteria 'starting date=empty'. And it turns out i get 0 results. When i delete those contacts from Zoho and import them again without that starting date column and then look them up with that custom view i get to see them fine.

So what i do right now is before importing i have to seperate the contacts with a starting date and import them separately from the others. Can this be fixed?