Minecraft does not create world icon if it is missing

Minecraft does not create a world icon if it is missing but also disables the "Reset Icon" button.

There are two cases in which a world can have no icon:

1. The world was generated in a previous version

2. You close the a newly generated world before entering:

   1. Create a new world

   2. Minimize Minecraft

   3. Open Minecraft after it finished generating the world and exit back to the main menu