No results in area alert

[pjdufour]

First...

• I've made sure there are no duplicate issues

Issue type

• bug report
• feature request

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If this is a feature request (if not, please remove this section)

Problem

Sometimes there simply no matches for a filter in an area, but you think the tiles are just taking a while to load.

Proposed Solution

After the loading tiles alert finishes. If no features were loaded, then show a "No Results in Area" alert.

Risks/concerns

Handling async nature of tile requests could quickly get out of hand, so important to scope this effort narrowly.