Drag & Drop in tree-view

Drag & dropping of expanded files causes the file to move to the parent directory.

Steps to reproduce:

1. expand a folder
2. Drag & drop one of the expanded files within the same region of other siblings.
3. It has now been moved up a folder i.e it is now a sibling of it's parent.

Expected behaviour: No changes to the file's location.

Additionally we should be able to move a file from one folder to another by dropping it in the region of expanded files.