Site user data doesn't want to sync

### Step 1: Please describe your environment

* ZeroNet version: 0.6.0 rev3179
* Operating system: w10 1607
* Web browser: currently Iridium, but other browsers show same results
* Tor status: doesn't seem to matter, currently as "available"
* Opened port: doesn't seem to matter, currently "opened" (opened in router settings)
* Special configuration: none that I'm aware of/that counts as special

### Step 2: Describe the problem:

Site data from [site id]/data/users/[user id]/*" doesn't want to sync

#### Steps to reproduce:

1. Send a letter thru zeromail to echbot/upload a song to ZeroLTSN

#### Observed Results:

* Zeromail: No reply from echo bot
* ZeroLTSN: No one gets the uploaded songs from me
* Common: sync error/missing file "data.json or content.json in data/users/[user id]/

#### Expected Results:

Everything should work fine (and works for others I've asked).

Reproduce the sync failure using the reported Zeromail or ZeroLTSN steps and inspect the affected data/users/[user id]/ path, especially the missing data.json or content.json files. Compare the local sync error with a working user's data and verify that the files arrive and the services receive the message or upload.

索引モデルが issue の本文から書いたものです。