SMP - When rescaling maps with paper, if you look at the map, you can no longer scale it

When the player is rescaling a map with paper, if they take out a map and look at it (looking at it to see what they've uncovered on it), the map can no longer be scaled.

To reproduce:
-Get paper
-Make a map
-Scale map once, then look at it
-You can no longer scale the map