OpenAPI CastAndValidate: filter out empty params

Closes #2198

CHANGELOG.md

@@ -37,6 +37,11 @@ switched to a new configuration mechanism, however it was not officially removed
 - Add documented-but-missing chat pagination.
 - Allow sending out emails again.
 
+## Unreleased (Patch)
+
+### Changed
+- API: Empty parameter values for integer parameters are now ignored in non-strict validaton mode.
+
 ## [2.1.2] - 2020-09-17
 
 ### Security

lib/pleroma/web/api_spec/cast_and_validate.ex

@@ -115,6 +115,10 @@ defp cast_and_validate(spec, operation, conn, content_type, false = _strict) do
             %{reason: :unexpected_field, name: name, path: [name]}, params ->
               Map.delete(params, name)
 
+            # Filter out empty params
+            %{reason: :invalid_type, path: [name_atom], value: ""}, params ->
+              Map.delete(params, to_string(name_atom))
+
             %{reason: :invalid_enum, name: nil, path: path, value: value}, params ->
               path = path |> Enum.reverse() |> tl() |> Enum.reverse() |> list_items_to_string()
               update_in(params, path, &List.delete(&1, value))