Download as Zip Not Working Correctly (rev3470, Windows 10, Firefox)

### Step 1: Please describe your environment

* ZeroNet version: 0.6.2 rev3470
* Operating system: Windows 10 Insider build 17672
* Web browser: Firefox
* Tor status: Error (actively refused)
* Opened port: yes
* Special configuration: None

### Step 2: Describe the problem:

Clicking Download as Zip in sidebar of a zite (I only tested this with ZeroTalk at the time) will download the zip. However, opening the zip with Windows Explorer will give the error "Windows cannot open the folder. The compressed (zipped) folder [name of file here] is invalid.". Furthermore, opening it in 7zip will only show the content.json file (even though the size of the zip file is shown to be 15MB).

Reproduce the issue by using the Download as Zip control in a ZeroTalk zite and opening the result with Windows Explorer or 7-Zip. Compare the archive contents with the reported 15MB size; done means the downloaded archive opens successfully and contains the expected zite files.

Written by the indexing model from the issue text.