修复首页bug

national-motion-module-system/national-motion-system-biz/src/main/java/org/jeecg/modules/system/app/mapper/xml/AppCoursesMapper.xml

@@ -250,9 +250,10 @@
     </select>
     <select id="getInstructorOrderCount" resultType="integer">
         SELECT
+            COALESCE(
             SUM((SELECT COUNT(*) FROM nm_order b
                  WHERE FIND_IN_SET(a.id, b.product_ids)
-            ))
+            )),0)
                 AS orderCount
         FROM nm_courses a WHERE a.user_id = #{id}
     </select>