Fixed ugly null pointer exception when there is no or incomplete root rule chain.

Make it go to an log entry instead.

application/src/main/java/org/thingsboard/server/actors/tenant/TenantActor.java

@@ -109,11 +109,15 @@ public class TenantActor extends RuleChainManagerActor {
     }
 
     private void onServiceToRuleEngineMsg(ServiceToRuleEngineMsg msg) {
+    	if (ruleChainManager.getRootChainActor()!=null)
         ruleChainManager.getRootChainActor().tell(msg, self());
+    	else logger.info("[{}] No Root Chain", msg);
     }
 
     private void onDeviceActorToRuleEngineMsg(DeviceActorToRuleEngineMsg msg) {
+    	if (ruleChainManager.getRootChainActor()!=null)
         ruleChainManager.getRootChainActor().tell(msg, self());
+    	else logger.info("[{}] No Root Chain", msg);
     }
 
     private void onRuleChainMsg(RuleChainToRuleChainMsg msg) {