scaffoldings with height 255 and bottom: true don't fall and disappear on right-click

steps to produce:

1. have a scaffolding with y = 255 (doesn't metter how)
2. put a scaffolding(s) near it (throught right-clicking with a scaffolding)
3. the scaffolding(s) near it won't fall, break, or be affected in any way. right-clicking them destroys them