Save errors when not using browse button

## When submitting an issue please include:
* 2.8.1
* Mac OS

### Steps to reproduce
* create new bag
* add some content
* click the "Save Bag As..." button
* type a path in "Save in:" field (DO NOT USE BROWSE BUTTON!)
* click "ok" button

### Expected results?
The bag was saved

### Actual result?
"Unexpected general bug" error pops up