Set empty sku not as new

Bug in update of an existing products over multiple store views.

| sku              | _type  | _attribute_set | _store | name | description | short_description |
|--------------------|-----------|----------------------|-----------|----------|------------------|---------------------------|
| existing_sku | simple | Default          |           | foo     | foo             | foo                     |
|                    |            |                     |  de     |bar      |bar              |bar                      |
|                    |            |                     |  en     |zoz     |zoz              |zoz                      |

\AvS_FastSimpleImport_Model_Import_Entity_Product_Type_Simple::_isSkuNew method will return *true* for second and third row. 
Magento will init a new product and add default values of attribute if set.
In my case i trigger the import method twice in a script. The first import adds new products and set some flags with yes/no options. The second import will "reinit" the values with the default value "0".
So the second import overwrites the values from first one.