SQL: add tests for 136854 (elastic#136935)

Follow-up to elastic#136854, just
adding a test

Author: luigidellaquila

x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/optimizer/OptimizerRunTests.java

@@ -223,6 +223,11 @@ public void testSimplifyComparisonArithmeticWithDateAndMultiplication() {
         );
     }
 
+    public void testIfNullPercentile() {
+        LogicalPlan p = plan("SELECT NULLIF(PERCENTILE(0+int+int, 50), 0) from test");
+        assertNotNull(p);
+    }
+
     private void doTestSimplifyComparisonArithmetics(String expression, String fieldName, String compSymbol, Object bound) {
         BinaryComparison bc = extractPlannedBinaryComparison(expression);
         assertEquals(compSymbol, bc.symbol());