[BUG] Data Import Tool - Data is getting lost.

[govindsmenokee]

Child table data is getting cleared on subsequent updates.

Example. On the Item Doctype initially I defined the Default Warehouse and Company and updated the default warehouse values(This worked)
Next I tried to download template to update the Default Supplier for this I downloaded the template with fields Company and Default Supplier (left out Default Warehouse)

On update the Default Supplier is getting set but now the Default Warehouse got cleared.

If you are giving the option to selectively import data into fields then this seems to be a bug which is critical because the update shows successful but now the end user has lost data.