module 'main' has no attribute 'file_server' in greenlet.py; AttributeError: 'Config' object has no attribute 'optional_limit'

### Step 1: Please describe your environment

* ZeroNet version: r4478
* Operating system: W10
* Web browser: FF

### Step 2: Describe the problem:

error lines in the debug.log:

> INFO - Libsecpk256k1 loaded: FFILibrary_U:\ZeroNet-win-dist-win64\lib\coincurve\libsecp256k1.dll in 0.859s
> ERROR - Unhandled exception: AttributeError: module 'main' has no attribute 'file_server' in greenlet.py line 766 > Chart/ChartCollector.py line 171 > 29
> ERROR - Unhandled exception: AttributeError: 'Config' object has no attribute 'optional_limit' in greenlet.py line 766 > core/src/util/helper.py line 234 > OptionalManager/ContentDbPlugin.py line 362 > 325
> INFO - Version: 0.7.1 r4478, Python 3.7.3 (v3.7.3:..., Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)], Gevent: 1.4.0

Start by reproducing the two exceptions from debug.log and inspect greenlet.py line 766, then trace the reported callers in Chart/ChartCollector.py line 171, core/src/util/helper.py line 234, and OptionalManager/ContentDbPlugin.py line 362. Done means both AttributeErrors are understood and no longer occur in the reported ZeroNet environment, with regression coverage where appropriate.

Written by the indexing model from the issue text.