fix: 避免空引用集合触发无效查询

- Agent 与 Skill 引用查询在空 ID 集合时直接返回

- 补充不调用 listByIds 的回归测试

easyflow-modules/easyflow-module-skill/src/main/java/tech/easyflow/skill/service/impl/SkillToolReferenceProviderImpl.java

@@ -69,6 +69,9 @@ public class SkillToolReferenceProviderImpl implements SkillToolReferenceProvide
                 ids.add(skill.getId());
             }
         }
+        if (ids.isEmpty()) {
+            return List.of();
+        }
         List<OfflineImpactBindingVo> result = new ArrayList<>();
         for (Skill skill : skillService.listByIds(ids)) {
             OfflineImpactBindingVo item = new OfflineImpactBindingVo();