Pass null as forEachFeatureAtPixel layer arg for unmanaged layers

[ahocevar]

Features on the removed ol.FeatureOverlay were detected by ol.Map#forEachFeatureAtPixel, and the layer arg passed to the handler function was null. This change makes it so the same behaviour applies to features on an unmanaged vector layer. Previously the forEachFeatureAtPixel handler was called with a reference to the unmanaged layer as layer arg.

See #4143 (comment).

Fixes #4114.

[ahocevar]

@bartvde, you may want to have a look to see how this affects #4114.

[bartvde]

#4114 is this still the same @ahocevar with this change
Assuming you mean if I still see the issue in your branch?

[ahocevar]

@bartvde I meant you should look at my branch to see if it makes your life easier, so you don't need a code snippet like the one you posted in your application.

Your issue is unlikely to be fixed with this branch, but it might. Because now forEachFeatureAtPixel is only called once for features that are on multiple unmanaged layers.

[ahocevar]

@bartvde I added a commit that fixes #4114. Please review.

[bartvde]

thanks @ahocevar I can confirm that this now fixes my issue from #4114
I'll do a review of the code tomorrow morning if no one gets to it before then.

[bartvde]

LGTM @ahocevar does this deserve a mention in the release notes?

[ahocevar]

I can add that, yes.

[ahocevar]

Done @bartvde.

[bartvde]

LGTM @ahocevar please merge if Travis agrees again