fix: 处理传递时间为空字符串的情况

yt-question/yt-question-service/src/main/java/com/ytpm/question/service/impl/AdServiceImpl.java

@@ -163,7 +163,7 @@ public class AdServiceImpl implements AdService {
     }
 
     private String verifyTimeParam(String fieldName, String value, String defaultValue) {
-        if (Objects.isNull(value) || "null".equals(value)) {
+        if (StrUtil.isEmpty(value) || "null".equals(value)) {
             if ("null".equals(value)) {
                 log.warn("param[{}] value '{}' is null !", fieldName, value);
             }