Fix ffmpeg framegrabs with Exile

changelog.d/framegrabs.fix

@@ -0,0 +1 @@
+Video framegrabs were not working correctly after the change to use Exile to execute ffmpeg

lib/pleroma/helpers/media_helper.ex

@@ -40,12 +40,14 @@ defmodule Pleroma.Helpers.MediaHelper do
   end
 
   # Note: video thumbnail is intentionally not resized (always has original dimensions)
+  @spec video_framegrab(String.t()) :: {:ok, binary()} | {:error, any()}
   def video_framegrab(url) do
     with executable when is_binary(executable) <- System.find_executable("ffmpeg"),
          {:ok, env} <- HTTP.get(url, [], pool: :media),
          {:ok, pid} <- StringIO.open(env.body) do
       body_stream = IO.binstream(pid, 1)
 
+      result =
         Exile.stream!(
           [
             executable,
@@ -62,6 +64,8 @@ defmodule Pleroma.Helpers.MediaHelper do
           stderr: :disable
         )
         |> Enum.into(<<>>)
+
+      {:ok, result}
     else
       nil -> {:error, {:ffmpeg, :command_not_found}}
       {:error, _} = error -> error