Update bestValue when futility pruning

In qsearch we should update the bestValue as we do
in case of futilityValue < beta, also when pruning
moves with non-positive see.

Spotted by Lucas Braesch

Bench: 5695710

src/search.cpp

@@ -1217,17 +1217,18 @@ namespace {
 
           if (futilityValue < beta)
           {
-              if (futilityValue > bestValue)
-                  bestValue = futilityValue;
-
+              bestValue = std::max(bestValue, futilityValue);
               continue;
           }
 
           // Prune moves with negative or equal SEE
           if (   futilityBase < beta
               && depth < DEPTH_ZERO
               && pos.see(move) <= 0)
+          {
+              bestValue = std::max(bestValue, futilityBase);
               continue;
+          }
       }
 
       // Detect non-capture evasions that are candidate to be pruned