Fix NPE if global setting implicit.host.tags is set to null (#8066)

Author: harikrishna-patnala

server/src/main/java/com/cloud/deploy/FirstFitPlanner.java

@@ -124,7 +124,7 @@ public class FirstFitPlanner extends AdapterBase implements DeploymentClusterPla
 
     protected String allocationAlgorithm = "random";
     protected String globalDeploymentPlanner = "FirstFitPlanner";
-    protected String[] implicitHostTags;
+    protected String[] implicitHostTags = new String[0];
 
     @Override
     public List<Long> orderClusters(VirtualMachineProfile vmProfile, DeploymentPlan plan, ExcludeList avoid) throws InsufficientServerCapacityException {
@@ -214,11 +214,11 @@ private void reorderClustersBasedOnImplicitTags(List<Long> clusterList, int requ
             Long uniqueTags;
             for (Long clusterId : clusterList) {
                 uniqueTags = (long) 0;
-            List<Long> hostList = capacityDao.listHostsWithEnoughCapacity(requiredCpu, requiredRam, clusterId, Host.Type.Routing.toString());
-            if (!hostList.isEmpty() && implicitHostTags.length > 0) {
-                uniqueTags = new Long(hostTagsDao.getDistinctImplicitHostTags(hostList, implicitHostTags).size());
-                uniqueTags = uniqueTags + getHostsByCapability(hostList, Host.HOST_UEFI_ENABLE);
-            }
+                List<Long> hostList = capacityDao.listHostsWithEnoughCapacity(requiredCpu, requiredRam, clusterId, Host.Type.Routing.toString());
+                if (!hostList.isEmpty() && implicitHostTags.length > 0) {
+                    uniqueTags = new Long(hostTagsDao.getDistinctImplicitHostTags(hostList, implicitHostTags).size());
+                    uniqueTags = uniqueTags + getHostsByCapability(hostList, Host.HOST_UEFI_ENABLE);
+                }
                 UniqueTagsInClusterMap.put(clusterId, uniqueTags);
             }
             Collections.sort(clusterList, new Comparator<Long>() {