Fix MetricDefinition mapper to return supportedAggregationTypes correctly (Azure#36708)

* Fix MetricDefinition mapper to return supportedAggregationTypes correctly

* Updating the CHANGELOG.md

* Updating the CHANGELOG.md

---------

Co-authored-by: Jair Myree (from Dev Box) <jairmyree@microsoft.com>

Author: matvey-mtn

sdk/monitor/azure-monitor-query/CHANGELOG.md

@@ -8,6 +8,9 @@
 
 ### Bugs Fixed
 
+- Fixed the issue with `MetricsQueryClient` and `MetricsQueryAsyncClient` where the `listMetricDefinitions` method was returning 
+`MetricsDefinition` objects with null values for `supportedAggregationTypes`.[(#36698)](https://github.com/Azure/azure-sdk-for-java/issues/36698)
+
 ### Other Changes
 
 ## 1.2.5 (2023-09-22)

sdk/monitor/azure-monitor-query/src/main/java/com/azure/monitor/query/implementation/metrics/models/MetricsHelper.java

@@ -180,7 +180,7 @@ public static MetricDefinition mapToMetricDefinition(com.azure.monitor.query.imp
             ? null
             : AggregationType.fromString(definition.getPrimaryAggregationType().toString());
         List<AggregationType> supportedAggregationTypes = null;
-        if (CoreUtils.isNullOrEmpty(definition.getSupportedAggregationTypes())) {
+        if (!CoreUtils.isNullOrEmpty(definition.getSupportedAggregationTypes())) {
             supportedAggregationTypes = definition.getSupportedAggregationTypes()
                 .stream()
                 .map(aggregationType -> AggregationType.fromString(aggregationType.toString()))