fix 云教练整合接口cbsDetail

mec-application/src/main/java/com/ym/mec/student/controller/StudentManageController.java

@@ -295,8 +295,11 @@ public class StudentManageController extends BaseController {
                 for (Map.Entry<Integer, String> entry : student.getExtSjectNamesMap().entrySet()) {
 
                     // 默认声部映射乐器ID
-                    String instrumentIds = collect.get(entry.getKey()).stream()
-                        .map(Instrument::getId).map(String::valueOf).collect(Collectors.joining(","));
+                    String instrumentIds = "";
+                    if (collect.containsKey(entry.getKey())) {
+                        instrumentIds = collect.get(entry.getKey()).stream()
+                            .map(Instrument::getId).map(String::valueOf).collect(Collectors.joining(","));
+                    }
 
                     // 萨克斯乐器，对应中音萨克斯
                     if (entry.getKey() == 5 || entry.getKey() == 6) {