update failed

### Step 1: Please describe your environment

* ZeroNet version: 0.6.2（3408）
* Operating system: _windows 10 1803
* Web browser: Firefox 59.0.3 x64
* Tor status: disabled
* Opened port: no
* Special configuration: no

### Step 2: Describe the problem:

#### Steps to reproduce:

1. blog always update failed
2. storage limitation have been set 9999 mb

#### Observed Results:

* What happened? This could be a screenshot, a description, log output (you can send log/debug.log file to hello@zeronet.io if necessary), etc.

#### Expected Results:

* What did you expect to happen?

No source file, test, log, or actionable expected result is identified. Start by reproducing the blog update failure with the listed ZeroNet, Windows, Firefox, and storage-limit settings, then use the resulting diagnostic output to locate the responsible update path; done means identifying and fixing the failure with a regression test.

索引モデルが issue の本文から書いたものです。