Native event seatbid.bid.ext.prebid.events.imp is not notified

[ValentinPostindustria]

Impression event seatbid.bid.ext.prebid.events.imp is not notified when adm doesn't have eventtrackers. It must be notified even if there are no eventtrackers.

ImpressionTracker is created in line 301 (PrebidNativeAd.java) only if there is at least one impression tracker (array imp_trackers).

if (imp_trackers != null) {
   ...
}

If there are no impression trackers we need to create ImpressionTracker with impEvent URL to call the notifyImpressionEvent() when an ad is on display.