multiple local geocoder search results broken

[andrewharvey]

As reported at https://stackoverflow.com/questions/56579673/why-does-supplemental-mapbox-geocoder-allow-for-only-one-search in the example at https://docs.mapbox.com/mapbox-gl-js/example/forward-geocode-custom-data/ if you:

1. Search and select Lincoln Park
2. Search and select Burnham Park.

Upon 2, it doesn't actually move to Burnham park, which it should.

[andrewharvey]

It looks like the issue could be around

mapbox-gl-geocoder/lib/index.js

Line 275 in af44fb0

if (selected && selected.id !== this.lastSelected) {

since localGeocoder sources may not have an id per feature set, we could either disable that where no id exists, or generate our own internal ids.

[scottsfarley93]

This looks to be the same as #278. It seems that the result event is not being emitted on subsequent selections from the local geocoder.

@andrewharvey good point about the potential lack of IDs from the localGeocoder. As you point out, I could see how the lack of IDs could cause no result event to be generated.

[scottsfarley93]

This was fixed in #298 and will be included in the upcoming v4.5.0 release.