Water plugin: editor defaults for water wave assets are not saved

• Enable the water plugin if it isn't already
• In project settings go to Plugins/Water Editor
• Edit either the default lake or ocean water wave asset
• Close the editor
• Reopen the editor

Expected result:

• The property is still set to the new asset and is saved in DefaultEngine.ini

Actual result:

• The property is reset to the plugin default and DefaultEngine.ini is unchanged