The empty array values should be treated as null value when parsing j…

…son data (#1044)

elasticsearch/src/main/java/com/amazon/opendistroforelasticsearch/sql/elasticsearch/data/utils/ElasticsearchJsonContent.java

@@ -90,7 +90,7 @@ public Iterator<? extends Content> array() {
 
   @Override
   public boolean isNull() {
-    return value == null || value.isNull();
+    return value == null || value.isNull() || (value.isArray() && value.isEmpty());
   }
 
   @Override

elasticsearch/src/test/java/com/amazon/opendistroforelasticsearch/sql/elasticsearch/data/value/ElasticsearchExprValueFactoryTest.java

@@ -105,6 +105,11 @@ public void constructNullValue() {
     assertTrue(new ElasticsearchJsonContent(null).isNull());
   }
 
+  @Test
+  public void constructNullArrayValue() {
+    assertEquals(nullValue(), tupleValue("{\"intV\":[]}").get("intV"));
+  }
+
   @Test
   public void constructByte() {
     assertEquals(byteValue((byte) 1), tupleValue("{\"byteV\":1}").get("byteV"));