Havannah: invalid detection of a ring

[PolarGo]

output:

genmove b 5
time: remain: 0, use: 5, sims: 0
Finished: 1 runs in 0 msec: 17549 Games/s
Solved as a win
PV: d3
Nodes before: 7232, after: 0, saved 0% of the tree

-> d3

           A B C D E F G H
         1 @ . . . . . . . I
        2 @ . @ X . . . . . J
       3 . @ X[X]X X . . . . K
      4 . . @ X X X . . . . . L
     5 . . . . . X . . . . . . M
    6 . . . @ . . . . . . . . . N
   7 . @ @ . . . . . . . . . . . O
  8 @ . . . . . . . . . . . . . . 
   9 . . . . . . . . . . . . . . 
   10 . . . . . . . . . . . . . 
    11 . . . . . . . . . . . . 
     12 . . . . . . . . . . . 
      13 . . . . . . . . . . 
       14 . . . . . . . . . 
        15 . . . . . . . . 

the game was
size 8
w a2
b e4
w c4
genmove b 3 => d4
w c7
genmove b 3 => c3
w b3
genmove b 6 => e3
w a1
genmove b 6 => f5
w a8
genmove b 6 => d2
w c2
genmove b 5 => f3
w d6
genmove b 5 => f4
w b7
genmove b 5 => d3

and claims a win for X (black), although it is not; no cell is completely surrounded

(definition of a ring is:
"A ring is a chain of stones around at least one cell (regardless of its being vacant or not).")