End portal blocks destroyed by water source

End portal blocks can be destroyed by pouring out a water bucket onto the appropriate side of the adjacent end portal frame (or another block). I did this accidentally while attempting to move mobs into the End. If all the portal blocks are destroyed, End access is impossible.

What I expected to happen was:
Either the water is poured on top of the portal blocks or nothing occurs.

What actually happened was:
The poured water replaced and destroyed the End portal block.