fix time convert bug

@@ -126,15 +126,20 @@ public class DeliveryMinutesService {
 
     private static int getMinutes(LimitTime limitTime){
         int minutes;
-        switch (limitTime.getTimeUnit()){
+        TimeUnit timeUnit;
+        if (Objects.nonNull(timeUnit=limitTime.getTimeUnit())) {
+            switch (timeUnit) {
                 case HOURS:
                 default:
-                minutes = limitTime.getLimitTime()*60;
+                    minutes = limitTime.getLimitTime() * 60;
                     break;
                 case MINUTES:
                     minutes = limitTime.getLimitTime();
                     break;
             }
+        }else{
+            minutes = limitTime.getLimitTime() * 60;
+        }
         return minutes;
     }