Settings for photo gallery fields are showing PHP warnings (ACF 6.1.4)

When configuring a new photo gallery field, or editing an existing one, I’m seeing several PHP warnings similar to this:

Warning: Undefined array key “fields[my_gallery” in \wp-content\plugins\navz-photo-gallery\includes\v5\render_field_settings.php on line 17

Warning: Trying to access array offset on value of type null in \wp-content\plugins\navz-photo-gallery\includes\v5\render_field_settings.php on line 23

This is the case across several sites using the plugin. It looks like ACF 6 has made some changes to the way settings fields are handled: https://www.advancedcustomfields.com/resources/adding-custom-settings-fields/#upgrade-existing-field-settings

It doesn’t seem to affect functionality of the settings for the fields, so it’s not really an issue on production sites with error reporting turned off, but it may be a good idea to take a look before future changes make it a problem.