Fixed NPE with reservataion start time and end time
diff --git a/modules/registry/registry-core/src/main/java/org/apache/airavata/registry/core/app/catalog/util/AppCatalogThriftConversion.java b/modules/registry/registry-core/src/main/java/org/apache/airavata/registry/core/app/catalog/util/AppCatalogThriftConversion.java
index 4d73ac6..8b40d62 100644
--- a/modules/registry/registry-core/src/main/java/org/apache/airavata/registry/core/app/catalog/util/AppCatalogThriftConversion.java
+++ b/modules/registry/registry-core/src/main/java/org/apache/airavata/registry/core/app/catalog/util/AppCatalogThriftConversion.java
@@ -834,8 +834,13 @@
         preference.setUsageReportingGatewayId(resource.getGatewayId());
         preference.setQualityOfService(resource.getQualityOfService());
         preference.setReservation(resource.getReservation());
-        preference.setReservationStartTime(resource.getReservationStartTime().getTime());
-        preference.setReservationEndTime(resource.getReservationEndTime().getTime());
+        if (resource.getReservationStartTime() != null) {
+            preference.setReservationStartTime(resource.getReservationStartTime().getTime());
+        }
+
+        if (resource.getReservationEndTime() != null) {
+            preference.setReservationEndTime(resource.getReservationEndTime().getTime());
+        }
         return preference;
     }