[CALCITE-4757] In Avatica, support columns of type "NULL" in query results

The bug was fixed in Avatica, and here we add tests to
Calcite now that we have upgraded to Avatica 1.19.

Close apache/calcite#2507
diff --git a/core/src/test/java/org/apache/calcite/test/JdbcTest.java b/core/src/test/java/org/apache/calcite/test/JdbcTest.java
index 19804b6..251555b 100644
--- a/core/src/test/java/org/apache/calcite/test/JdbcTest.java
+++ b/core/src/test/java/org/apache/calcite/test/JdbcTest.java
@@ -3462,6 +3462,21 @@
             + "EXPR$0=250\n");
   }
 
+  @Test void testSelectValuesIncludeNull() {
+    CalciteAssert.that()
+        .query("select * from (values (null))")
+        .returns("EXPR$0=null\n");
+  }
+
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-4757">[CALCITE-4757]
+   * In Avatica, support columns of type "NULL" in query results</a>. */
+  @Test void testSelectValuesIncludeNull2() {
+    CalciteAssert.that()
+        .query("select * from (values (null, true))")
+        .returns("EXPR$0=null; EXPR$1=true\n");
+  }
+
   @Test void testSelectDistinct() {
     CalciteAssert.hr()
         .query("select distinct \"deptno\"\n"