Reset negative statScore on fail high

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 9073 W: 1937 L: 1766 D: 5370

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 53530 W: 8139 L: 7823 D: 37568

Bench: 5170165

Author: VoyagerOne

src/search.cpp

@@ -1085,6 +1085,7 @@ namespace {
               else
               {
                   assert(value >= beta); // Fail high
+                  ss->statScore = std::max(ss->statScore, 0);
                   break;
               }
           }