🐛 Fix IndexOutOfRangeException when ply >= MaxDepth

[eduherminio]

[-5, 0]

Score of Lynx 1242 - depth-overflow vs Lynx 1239 - main: 3616 - 3601 - 2393  [0.501] 9610
...      Lynx 1242 - depth-overflow playing White: 2155 - 1444 - 1205  [0.574] 4804
...      Lynx 1242 - depth-overflow playing Black: 1461 - 2157 - 1188  [0.428] 4806
...      White vs Black: 4312 - 2905 - 2393  [0.573] 9610
Elo difference: 0.5 +/- 6.0, LOS: 57.0 %, DrawRatio: 24.9 %
SPRT: llr 1.61 (54.8%), lbound -2.94, ubound 2.94