comparator reading full cauldron through a block does not update when removing cauldron

when a comparator is reading the status of a cauldron through a block and the cauldron is removed, the comparator fails to update and stays powered.

to reproduce:
place a cauldron and fill it with water
place a block behind it
place a comparator behind that block, facing away from the cauldron
the comparator is now powered, as it should
remove the cauldron

expectation: the comparator turns it's output off

actual behavior: the comparator stays powered until it is updated