ark can overwite files without warning

[Juha Lahti]

If archive root contains folder and it is extracted into folder which contains normal file with the same name as folder, ark silently overwrites the original file.

Steps to reproduce problem:

1. Create archive which contains folder "test".

2. create normal file "test" somewhere.

3. Extract archive into the same folder as "test" file. Ark does not even show the normal file in the destination selection.

4. Normal file is silently overwritten without any warning or notification.

Tested in:

Ubuntu 18.04 LTS
ark 4:17.12.3-0ubuntu1