File > New fails silently if folder is read-only

[peterflynn]

Steps:

1. Create a folder that you do not have write access to (i.e. that you cannot create new files within)
2. Point Brackets at this folder
3. File > New
4. (optional) Type a new file name
5. Hit Enter

Result:
The new item in the folder tree disappears. No file is created or opened in the editor, but no error message is shown either.

Expected:
Error dialog appears.

[gruehle]

Back to Peter to confirm and close.

[peterflynn]

Verified this fix works with my read-only network share, and with a local folder where my user permissions do not allow write access. Closing...