fix(hero): 修复DamageQueueComp中caster可能为null时的错误

当caster或caster.ent为null时，使用可选链操作符和空值合并运算符提供默认值，避免生成eventId时出现错误

assets/script/game/hero/DamageQueueComp.ts

@@ -60,7 +60,8 @@ export class DamageQueueComp extends ecs.Comp {
      */
     addDamageEvent(attrs: any, caster: HeroViewComp, s_uuid: number,ext_dmg:number=0,dmg_ratio:number=1): void {
         const timestamp = Date.now();
-        const eventId = `${caster.ent.eid}_${s_uuid}_${timestamp}_${Math.random()}`;
+        const casterEid = caster?.ent?.eid ?? -1;
+        const eventId = `${casterEid}_${s_uuid}_${timestamp}_${Math.random()}`;
         
         const damageEvent: DamageEvent = {
             Attrs: attrs ? { ...attrs } : null, // 深拷贝属性数据