when you place a ladder-not on the side of a block, but just right clicking the ground with a ladder- causes the game to crash, but only if there was previously a flower pot there.-
1.place a flower pot.
2.then remove it and right click the block that the flower pot was on with a ladder.
I can confirm this although it seems to have nothing to do with flower pots. To reproduce:
1. Hold a ladder
2. Click with it on a "floor block" next to a "wall block"
3 Crash
Will not crash if you click on the bottom "wall block" instead.
Will not crash if you click on a "floor block" that doesn't have a "wall block" beside it.