fix(wither): move livingEntitySelector from static to per-instance

Withers were previously using the same static LES pointer (which gets destroyed on death) causing a segfault when another wither is spawned after the first one is dead

targets/minecraft/world/entity/boss/wither/WitherBoss.cpp

@@ -51,9 +51,9 @@ bool LivingEntitySelector::matches(std::shared_ptr<Entity> entity) const {
     }
 }
 
-EntitySelector* WitherBoss::livingEntitySelector = new LivingEntitySelector();
-
 WitherBoss::WitherBoss(Level* level) : Monster(level) {
+    // 4jcraft: moved to per-instance
+    livingEntitySelector = new LivingEntitySelector();
     // 4J Stu - This function call had to be moved here from the Entity ctor to
     // ensure that the derived version of the function is called
     this->defineSynchedData();

targets/minecraft/world/entity/boss/wither/WitherBoss.h

@@ -43,7 +43,8 @@ private:
     int idleHeadUpdates[IDLE_HEAD_UPDATES_SIZE];
     int destroyBlocksTick;
 
-    static EntitySelector* livingEntitySelector;
+    // 4jcraft: moved to per-instance
+    EntitySelector* livingEntitySelector;
 
 public:
     WitherBoss(Level* level);