From a3a7178b604d8bc589a8e3ac06abac094cce5e17 Mon Sep 17 00:00:00 2001
From: lain <lain@soykaf.club>
Date: Tue, 4 Jun 2019 13:58:36 +0200
Subject: [PATCH] Participations: Filter out participations without activities.

---
 lib/pleroma/conversation/participation.ex |  1 +
 test/conversation/participation_test.exs  | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/lib/pleroma/conversation/participation.ex b/lib/pleroma/conversation/participation.ex
index 2a11f9069..2c13c4b40 100644
--- a/lib/pleroma/conversation/participation.ex
+++ b/lib/pleroma/conversation/participation.ex
@@ -79,5 +79,6 @@ defmodule Pleroma.Conversation.Participation do
         | last_activity_id: activity_id
       }
     end)
+    |> Enum.filter(& &1.last_activity_id)
   end
 end
diff --git a/test/conversation/participation_test.exs b/test/conversation/participation_test.exs
index 568953b07..0e60bfca5 100644
--- a/test/conversation/participation_test.exs
+++ b/test/conversation/participation_test.exs
@@ -86,4 +86,17 @@ defmodule Pleroma.Conversation.ParticipationTest do
 
     assert participation_one.last_activity_id == activity_three.id
   end
+
+  test "Doesn't die when the conversation gets empty" do
+    user = insert(:user)
+
+    {:ok, activity} = CommonAPI.post(user, %{"status" => ".", "visibility" => "direct"})
+    [participation] = Participation.for_user_with_last_activity_id(user)
+
+    assert participation.last_activity_id == activity.id
+
+    {:ok, _} = CommonAPI.delete(activity.id, user)
+
+    [] = Participation.for_user_with_last_activity_id(user)
+  end
 end