Setting initial value for last_request_date for feed clusters. (#2072)

There was a change introduced in CV2-5331 that normalized how the `last_request_date` field for a shared feed cluster is calculated. But there is an issue: if the cluster doesn't have any request, no value is set. The fix needed here is to be sure that there is an initial value, which can be the same date as the last item that joined the cluster, when this item has no requests.

Fixes: CV2-5446.

lib/tasks/check_khousheh.rake

@@ -278,7 +278,7 @@ namespace :check do
                     updated_cluster_attributes[:channels] = (cluster.channels.to_a + pm.channel.to_h['others'].to_a + [pm.channel.to_h['main']]).uniq.compact_blank
                     updated_cluster_attributes[:media_count] = cluster.media_count + 1
                     updated_cluster_attributes[:requests_count] = cluster.requests_count + pm.requests_count
-                    updated_cluster_attributes[:last_request_date] = (pm.tipline_requests.last&.created_at.to_i > cluster.last_request_date.to_i) ? pm.tipline_requests.last.created_at : cluster.last_request_date
+                    updated_cluster_attributes[:last_request_date] = (pm.tipline_requests.last&.created_at.to_i > cluster.last_request_date.to_i) ? pm.tipline_requests.last.created_at : (cluster.last_request_date || Time.at(pm.last_seen))
                     updated_cluster_attributes[:fact_checks_count] = cluster.fact_checks_count
                     updated_cluster_attributes[:last_fact_check_date] = cluster.last_fact_check_date
                     unless pm_fc_mapping[pm.id].blank?