Fix dashboard notification when set rocketmq.config.enableDashBoardCollect=false (#679)

Co-authored-by: zhangxu16 <zhangxu16@xiaomi.com>
diff --git a/rocketmq-console/src/main/java/org/apache/rocketmq/console/service/impl/DashboardCollectServiceImpl.java b/rocketmq-console/src/main/java/org/apache/rocketmq/console/service/impl/DashboardCollectServiceImpl.java
index a3f7d73..2a895dd 100644
--- a/rocketmq-console/src/main/java/org/apache/rocketmq/console/service/impl/DashboardCollectServiceImpl.java
+++ b/rocketmq-console/src/main/java/org/apache/rocketmq/console/service/impl/DashboardCollectServiceImpl.java
@@ -36,7 +36,6 @@
 import java.util.Set;
 import javax.annotation.Resource;
 import org.apache.rocketmq.console.config.RMQConfigure;
-import org.apache.rocketmq.console.exception.ServiceException;
 import org.apache.rocketmq.console.service.DashboardCollectService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -137,7 +136,8 @@
         String dataLocationPath = rmqConfigure.getConsoleCollectData();
         File file = new File(dataLocationPath + date + ".json");
         if (!file.exists()) {
-            throw Throwables.propagate(new ServiceException(1, "This date have't data!"));
+            log.info(String.format("No dashboard data for broker cache data: %s", date));
+            return Maps.newHashMap();
         }
         return jsonDataFile2map(file);
     }