Warning Menu when import generation data for a new world does not react when click "Yes"

When I use the import settings function to create a new world ("Create new World" -> "More World Options..." -> "Import Settings") and selected a file in the correct format, I get a warning says that these settings are experimental. But when I click on "Yes", the menu is still open until i click on "No". The settings from the file are still used when i click "Yes" (and than "No" to close the menu) but the warning shoud directly disapper when cllick on "Yes". (The settings are not used when i click directly "No" without clicking "Yes" before. This is already right)