feature/CSTACKEX-220: null check for volumeToAttach (#81)

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### Types of changes

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Co-authored-by: Srivastava, Piyush <Piyush.Srivastava@netapp.com>

Author: piyush5netapp

plugins/storage/volume/ontap/src/main/java/org/apache/cloudstack/storage/lifecycle/OntapPrimaryDatastoreLifecycle.java

@@ -340,7 +340,7 @@ public boolean attachZone(DataStore dataStore, ZoneScope scope, Hypervisor.Hyper
             logger.error("attachZone : Storage Pool not found for id: " + dataStore.getId());
             throw new CloudRuntimeException("Storage Pool not found for id: " + dataStore.getId());
         }
-        if (!Hypervisor.HypervisorType.KVM.equals(hypervisorType)){
+        if (!Hypervisor.HypervisorType.KVM.equals(hypervisorType)) {
             logger.error("attachZone : ONTAP primary storage is supported only for KVM hypervisor");
             throw new CloudRuntimeException("ONTAP primary storage is supported only for KVM hypervisor");
         }

server/src/main/java/com/cloud/storage/VolumeApiServiceImpl.java

@@ -4852,7 +4852,7 @@ private VolumeVO sendAttachVolumeCommand(UserVmVO vm, VolumeVO volumeToAttach, L
                 // Reload volume from DB after grantAccess — managed storage drivers (e.g. ONTAP)
                 // may update the volume's path and iScsiName during grantAccess, so the local
                 // volumeToAttach object can be stale.
-                if(DataStoreProvider.ONTAP_PLUGIN_NAME.equals(volumeToAttachStoragePool.getStorageProviderName())){
+                if (volumeToAttachStoragePool != null && DataStoreProvider.ONTAP_PLUGIN_NAME.equals(volumeToAttachStoragePool.getStorageProviderName())) {
                     volumeToAttach = _volsDao.findById(volumeToAttach.getId());
                 }
             }