ObjectValidators.Types.ObjectID: Fix when URI.parse returns %URL{host: ""}

lib/pleroma/web/activity_pub/object_validators/types/object_id.ex

@@ -6,14 +6,10 @@ def type, do: :string
   def cast(object) when is_binary(object) do
     # Host has to be present and scheme has to be an http scheme (for now)
     case URI.parse(object) do
-      %URI{host: nil} ->
-        :error
-
-      %URI{scheme: scheme} when scheme in ["https", "http"] ->
-        {:ok, object}
-
-      _ ->
-        :error
+      %URI{host: nil} -> :error
+      %URI{host: ""} -> :error
+      %URI{scheme: scheme} when scheme in ["https", "http"] -> {:ok, object}
+      _ -> :error
     end
   end