fix 导入学生时不传学号的时候报错的bug (BUG #3980)

server-db/src/main/java/cn/exploring/engine/server/db/service/StudentInfoService.java

@@ -312,7 +312,8 @@ public class StudentInfoService {
     }
 
     public List<StudentInfoExcelImportResultVo> checkImportByExcel(Collection<StudentInfoExcelImportVo> importVoList, Integer classId) {
-        Map<String, StudentInfo> existStudent = selectStudentInfoByUniqueId(importVoList.stream().map(StudentInfoExcelImportVo::getStudentUid).filter(org.apache.commons.lang3.StringUtils::isNotBlank).collect(Collectors.toSet()))
+        Set<String> studentUidSet = importVoList.stream().map(StudentInfoExcelImportVo::getStudentUid).filter(StringUtils::isNotBlank).collect(Collectors.toSet());
+        Map<String, StudentInfo> existStudent = CollectionUtils.isEmpty(studentUidSet) ? Collections.emptyMap() : selectStudentInfoByUniqueId(studentUidSet)
                 .stream().collect(Collectors.toMap(StudentInfo::getStudentUniqueId, x -> x, (k1, k2) -> k1));
 
         Set<String> duplicateStudentUid = importVoList.stream()