added check for calculatino result and fixed issue when current entity set as ref entity

application/src/main/java/org/thingsboard/server/actors/calculatedField/CalculatedFieldEntityMessageProcessor.java

@@ -287,7 +287,9 @@ public class CalculatedFieldEntityMessageProcessor extends AbstractContextAwareM
                 state.checkStateSize(ctxId, ctx.getMaxStateSize());
                 stateSizeChecked = true;
                 if (state.isSizeOk()) {
-                    cfService.pushMsgToRuleEngine(tenantId, entityId, calculationResult, cfIdList, callback);
+                    if (!calculationResult.isEmpty()) {
+                        cfService.pushMsgToRuleEngine(tenantId, entityId, calculationResult, cfIdList, callback);
+                    }
                     if (DebugModeUtil.isDebugAllAvailable(ctx.getCalculatedField())) {
                         systemContext.persistCalculatedFieldDebugEvent(tenantId, ctx.getCfId(), entityId, state.getArguments(), tbMsgId, tbMsgType, JacksonUtil.writeValueAsString(calculationResult.getResult()), null);
                     }

application/src/main/java/org/thingsboard/server/service/cf/CalculatedFieldResult.java

@@ -27,4 +27,11 @@ public final class CalculatedFieldResult {
     private final AttributeScope scope;
     private final JsonNode result;
 
+    public boolean isEmpty() {
+        return result == null || result.isMissingNode() || result.isNull() ||
+                (result.isObject() && result.isEmpty()) ||
+                (result.isArray() && result.isEmpty()) ||
+                (result.isTextual() && result.asText().isEmpty());
+    }
+
 }

application/src/main/java/org/thingsboard/server/service/cf/ctx/state/CalculatedFieldCtx.java

@@ -83,7 +83,7 @@ public class CalculatedFieldCtx {
         for (Map.Entry<String, Argument> entry : arguments.entrySet()) {
             var refId = entry.getValue().getRefEntityId();
             var refKey = entry.getValue().getRefEntityKey();
-            if (refId == null) {
+            if (refId == null || refId.equals(calculatedField.getEntityId())) {
                 mainEntityArguments.put(refKey, entry.getKey());
             } else {
                 linkedEntityArguments.computeIfAbsent(refId, key -> new HashMap<>()).put(refKey, entry.getKey());