Capture logic is incorrect when chains are involved

[blahedo]

When a user places a stone in the last empty intersection adjacent to a stone of the opposite colour, that stone is captured even if it's part of a chain that still has liberties. In this board the white chain at B8-C8 has, collectively, four liberties:

But after a single black placement at A8, the white stone at B8 is captured:

This is in game # 5797941e3a0ac6306cd86c11 .

[blahedo]

Oh! This is apparently on the UI side, not internally (see also bug #8); when the page is reloaded the white stone at B8 has reappeared and the black player's score has gone back down by one:

So somewhere the logic is correct, but the correct logic is not being used to update the UI.