[#4910] fixed config center response exception cause nullPointerException (#4912)

Author: chengyouling

clients/config-center-client/src/main/java/org/apache/servicecomb/config/center/client/ConfigCenterClient.java

@@ -147,7 +147,7 @@ public QueryConfigurationsResponse queryConfigurations(QueryConfigurationsReques
     } catch (IOException e) {
       addressManager.recordFailState(address);
       LOGGER.error("query configuration from {} failed, message={}", uri, e.getMessage());
-      throw new OperationException("", e);
+      throw new OperationException("query configuration failed!", e);
     }
   }
 

clients/config-center-client/src/main/java/org/apache/servicecomb/config/center/client/ConfigCenterManager.java

@@ -90,7 +90,7 @@ public void execute() {
         startTask(new BackOffSleepTask(configCenterConfiguration.getRefreshIntervalInMillis(), new PollConfigurationTask(0)));
       } catch (Exception e) {
         LOGGER.warn("get configurations from ConfigCenter failed, and will try again, cause message: {}. current "
-            + "fail does not affect the obtained historical configuration.", e.getCause().getMessage());
+            + "fail does not affect the obtained historical configuration.", e.getMessage());
         startTask(new BackOffSleepTask(failCount + 1, new PollConfigurationTask(failCount + 1)));
       }
     }

clients/config-kie-client/src/main/java/org/apache/servicecomb/config/kie/client/KieConfigManager.java

@@ -156,7 +156,7 @@ public void execute() {
         }
       } catch (Exception e) {
         LOGGER.warn("get configurations from KieConfigCenter failed, and will try again, cause message: {}. current "
-            + "fail does not affect the obtained historical configuration.", e.getCause().getMessage());
+            + "fail does not affect the obtained historical configuration.", e.getMessage());
         startTask(
             new BackOffSleepTask(failCount + 1, new PollConfigurationTask(failCount + 1, this.configurationsRequest)));
       }