[Maps] Unable to load Configured Tile Map Service

[nickpeihl]

Kibana version:
7.9.0-snapshot

Elasticsearch version:

Server OS version:
Cloud

Browser version:
Firefox 78.0.2
Browser OS version:
Mac Mojave 10.14.6

Original install method (e.g. download page, yum, from source, etc.):
In cloud

Describe the bug:
A tile service layer configured in kibana.yml can not be loaded in Maps. It causes JavaScript to freeze and lock up.

Steps to reproduce:

1. In kibana.yml add

map.tilemap.url: https://maps.wikimedia.org/osm-intl/{z}/{x}/{y}.png
map.tilemap.options.attribution: "[Wikimedia maps](https://wikimediafoundation.org/wiki/Maps_Terms_of_Use)|© [OpenStreetMap](http://www.openstreetmap.org/copyright)"
map.tilemap.options.maxZoom: 18

2. In Maps, try to add a Configured Tile Map Service
3. Kibana becomes frozen and the browser may report the webpage is slowing the browser.

Errors in browser console (if relevant):
Uncaught (in promise) Error: Minified React error #185; visit https://reactjs.org/docs/error-decoder.html?invariant=185 for the full message or use the non-minified dev environment for full errors and additional helpful warnings.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[kindsun]

Sounds like a dupe of #68818. Just fixed via #71946 but only merged 6 days ago. Closing for now but feel free to reopen if I'm wrong!