Fix: Parsing node files did not prefill missing fields correctly.
Fix: Parsing node files did not prefill missing fields correctly.

* This lead to a HTTP 500 on dashboard as some nodes were missing
monitoring fields.
* Removed a problematic cast and added sane defaults.

freifunkhamburg/ffffng,freifunkhamburg/ffffng,freifunkhamburg/ffffng,freifunkhamburg/ffffng