leaves disaper when i puch it with a piston

i was trying to push a leave with a piston for a x-ry maching
but when i did that the leave disaperd. i was pushing it with a sticky piston but i works also with a normal piston.

Steps to Reproduce:
1. Put a leave in front of a sticky/normal piston.
2. flik the liver to activate the piston.
3. and the leave disapers