Empty .OK file results in error message

In the latest 3.8 version, it is no longer possible to use an empty .OK file with the same filename as the single import file. Running the import results in 
```sh
 Can't read the content of file "/Users/wagnert/Workspace_Idea/techdivision/import-cli-simple/instances/ee/2.3.4/var/importexport/product-import_20161021-161909_01.ok"
```