Fix ModerationLog FunctionClauseError for unknown actions

Add catchall clause to handle log entries with unknown actions or
malformed data. Prevents HTTP 500 errors in admin moderation log view.

Fixes #3385

lib/pleroma/moderation_log.ex

@@ -575,6 +575,12 @@ defmodule Pleroma.ModerationLog do
     "@#{actor_nickname} requested account backup for @#{user_nickname}"
   end
 
+  def get_log_entry_message(%ModerationLog{data: data}) do
+    actor_name = get_in(data, ["actor", "nickname"]) || "unknown"
+    action = data["action"] || "unknown"
+    "@#{actor_name} performed action #{action}"
+  end
+
   defp nicknames_to_string(nicknames) do
     nicknames
     |> Enum.map(&"@#{&1}")

test/pleroma/moderation_log_test.exs

@@ -308,4 +308,37 @@ defmodule Pleroma.ModerationLogTest do
       assert log.data["message"] == "@#{moderator.nickname} deleted status ##{note.id}"
     end
   end
+
+  describe "get_log_entry_message/1" do
+    setup do
+      moderator = insert(:user, is_moderator: true)
+      [moderator: moderator]
+    end
+
+    test "handles unknown action types gracefully", %{moderator: moderator} do
+      log_entry = %ModerationLog{
+        data: %{
+          "actor" => %{"nickname" => moderator.nickname},
+          "action" => "unknown_action",
+          "some_data" => "test_value"
+        }
+      }
+
+      assert ModerationLog.get_log_entry_message(log_entry) =~ moderator.nickname
+      assert ModerationLog.get_log_entry_message(log_entry) =~ "unknown_action"
+    end
+
+    test "handles malformed log entries gracefully" do
+      log_entry = %ModerationLog{
+        data: %{
+          "action" => "force_password_reset"
+          # Missing "actor" and "subject" fields
+        }
+      }
+
+      message = ModerationLog.get_log_entry_message(log_entry)
+      assert is_binary(message)
+      assert message =~ "force_password_reset"
+    end
+  end
 end