When you are in the crafting menu and put your resized map in your active slot it will show the map u opened the last time
Steps to reproduce:
1.Open an empty map
2.Put it in your active slot to look at it
3.Go in to a crafting table menu
4.Resize it with 8 pieces of paper
5.while still being in the menu put the map in your active slot
6. in the background u will see the map that is not resized.
7 if u lieave the menu it will resize
sorry for my bad english
Unable to reproduce. It now shows blank map when in active slot, until exciting crafting menu and/or moving item from active slot.