changed PH so that HP falls to 1 instead of 0, for PH only

src/potions/poison_health.cc

@@ -14,7 +14,7 @@ void poison_health::apply(const enum race &race, int &HP, int &ATK, int &DEF,
                 if (race == DROW)
                         tmp *= DROW_POTION_MUL;
 
-                HP = std::max(HP - tmp, 0);
+                HP = std::max(HP - tmp, 1);
                 --remaining_duration;
         }
 }