fix: npe

src/main/java/com/qqflow/engine/common/util/id/GenLong15Util.java

@@ -24,9 +24,9 @@ public class GenLong15Util {
     }
 
     private static void checkAndInit() {
-        if (machineCode == null) {
+        if (recordSecond == null) {
             synchronized (GenLong15Util.class) {
-                if (machineCode == null) {
+                if (recordSecond == null) {
                     initData();
                 }
             }