Empty Free Text field is having value '0' after generating a report

Hi,

I tried to generate a report where a dropdown value should be a specific value and a free text field is not null which I mentioned in the filter area but after generating the report I am getting the free text field value as '0' for those records which have this field value as null.

Is this the system behaviour?

Could anybody provide me the solution for this in order to get a report for the records which has the drop down field value as a specific value and a free text field which is not null?

Thanks