Fix pair update in stochastic entropy merging.

The old code simply did not make sense.
The effect is that the pair would be popped from the
queue no matter what; as the queue is small, it does
not matter that much on the results.
But it will matter for a later CL.

Change-Id: If50c9fa9d7f3ac3c48bb7336d81479287d4944c4
(cherry picked from commit 485ff86fbb174b518834503cb39c9c8e20567f38)
1 file changed