fix(config): skip ConfigDB settings for modules that no longer exist

Ported from Akkoma af7c3fab9; the rescue is in the Ecto type load so
admin input is still validated.

Co-authored-by: FloatingGhost <hannah@coffee-and-dreams.uk>

lib/pleroma/config/transfer_task.ex

@@ -48,6 +48,7 @@ defmodule Pleroma.Config.TransferTask do
       settings =
         (Repo.all(ConfigDB) ++ deleted_settings)
         |> Enum.reject(&ConfigDB.static?/1)
+        |> Enum.reject(&(&1.group == :invalid_atom or &1.key == :invalid_atom))
         |> Enum.map(&merge_with_default/1)
 
       started_applications = Application.started_applications()

lib/pleroma/ecto_type/config/atom.ex

@@ -5,6 +5,8 @@
 defmodule Pleroma.EctoType.Config.Atom do
   use Ecto.Type
 
+  require Logger
+
   def type, do: :atom
 
   def cast(key) when is_atom(key) do
@@ -17,8 +19,17 @@ defmodule Pleroma.EctoType.Config.Atom do
 
   def cast(_), do: :error
 
+  # A key or group naming a module that no longer exists (e.g. a removed uploader)
+  # must not crash loading
   def load(key) do
     {:ok, Pleroma.ConfigDB.string_to_elixir_types(key)}
+  rescue
+    ArgumentError ->
+      Logger.warning(
+        "ConfigDB: unknown module #{key} in a setting key or group, the setting is not applied"
+      )
+
+      {:ok, :invalid_atom}
   end
 
   def dump(key) when is_atom(key), do: {:ok, inspect(key)}