修复导出附件所属学科专业类字段问题

server/cloud/tbook/func-tbook-export.js

@@ -304,7 +304,7 @@ function fixVolumeData(json,volumeData,index,totalJson){
     json.uQT = circleCheck[(volumeData?.unitType?.indexOf("其他")>-1)?1:0];
     json.dc4 = disciplineCode4;
     json.dn4 = disciplineName4;
-    json.mc4 = majorCode4;
+    json.mc4 = disciplineCode4;
     json.mn4 = majorName4;
     json.majorCodePad = majorCode4;
     json.mc6 = majorCode6;