This allows more diverse representation of the error subject at a glance
than relying on colour alone.
However, it would be good to have a generic error icon that can contain
icons which is differentiated from the point icon for clarity.
Sidebar header currently still uses the bolt icon until I figure out
how to deal with that. Also the font awesome icons don't seem to work,
perhaps there's additional code needed for those that I've missed.
This could result in error updates getting aborted when new errors are
loaded as their individual ids are never going to match tile IDs (see
`abortUnwantedRequests` function).