Change QTFastStart to recover gracefully if it encounters an error during bitstring matching

This fixes issues with internal errors when trying to serve the video

changelog.d/qtfaststart.fix

@@ -0,0 +1 @@
+MediaProxy Preview failures prevented when encountering certain video files

lib/pleroma/helpers/qt_fast_start.ex

@@ -40,16 +40,21 @@ defmodule Pleroma.Helpers.QtFastStart do
          got_mdat,
          acc
        ) do
-    full_size = (size - 8) * 8
+    try do
-    <<data::bits-size(full_size), rest::bits>> = rest
+      full_size = (size - 8) * 8
+      <<data::bits-size(full_size), rest::bits>> = rest
 
-    acc = [
+      acc = [
-      {fourcc, pos, pos + size, size,
+        {fourcc, pos, pos + size, size,
-       <<size::integer-big-size(32), fourcc::bits-size(32), data::bits>>}
+         <<size::integer-big-size(32), fourcc::bits-size(32), data::bits>>}
-      | acc
+        | acc
-    ]
+      ]
 
-    fix(rest, pos + size, got_moov || fourcc == "moov", got_mdat || fourcc == "mdat", acc)
+      fix(rest, pos + size, got_moov || fourcc == "moov", got_mdat || fourcc == "mdat", acc)
+    rescue
+      _ ->
+        :abort
+    end
   end
 
   defp fix(<<>>, _pos, _, _, acc) do