Restore path stripping problem

Hello Ziirish,

I found a couple of issues in Burp-UI which I just started playing with and which I love!

When trying to Download Selected files from a Windows backup:

1. When the downloaded file is opened with the default Zip browser in Windows 7, the file shows empty. Opening it with another archiver (e.g. WinRAR) works fine and I can browse the zip to the file(s) that were restored. I suspect this is because the Windows 7 Zip browser cannot handle a zip file that had D:, a drive letter, at the top of the tree
2. Related to this, I tried to strip the first part of the path from using the 'Number of leading path components to strip:' feature of 'Download Selected Files'. When I tried to download, I got 'Internal Server error' and the following debug log:

File "/usr/local/lib/python2.7/dist-packages/burpui/misc/backend/burp1.py", line 922, in restore_files
    if strip and strip.isdigit() and int(strip) > 0:
AttributeError: 'int' object has no attribute 'isdigit'

When I forced strip to be a string with: s = str(args['strip']) on line 84 of burpui/api/restore.py I was able to restore without the initial D:

I suspect this is not the best way to fix this but I'm letting you know.

Thanks for putting so much work into Burp-UI - looks great!!

Take care,

Jerry.