Fix NPE on list hosts, when any stale entries exists on storage_pool_host_ref for the removed pools

Author: sureshanaparti

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

@@ -504,7 +504,7 @@ public boolean isLocalStorageActiveOnHost(Long hostId) {
         List<StoragePoolHostVO> storagePoolHostRefs = _storagePoolHostDao.listByHostId(hostId);
         for (StoragePoolHostVO storagePoolHostRef : storagePoolHostRefs) {
             StoragePoolVO PrimaryDataStoreVO = _storagePoolDao.findById(storagePoolHostRef.getPoolId());
-            if (PrimaryDataStoreVO.getPoolType() == StoragePoolType.LVM || PrimaryDataStoreVO.getPoolType() == StoragePoolType.EXT) {
+            if (PrimaryDataStoreVO != null && (PrimaryDataStoreVO.getPoolType() == StoragePoolType.LVM || PrimaryDataStoreVO.getPoolType() == StoragePoolType.EXT)) {
                 SearchBuilder<VolumeVO> volumeSB = volumeDao.createSearchBuilder();
                 volumeSB.and("poolId", volumeSB.entity().getPoolId(), SearchCriteria.Op.EQ);
                 volumeSB.and("removed", volumeSB.entity().getRemoved(), SearchCriteria.Op.NULL);