JPA-31 - Simple JPQL with guarded null Parameter fails with Postgresql

Add test case to prove the issue does not replicate

hibernate-core/src/test/java/org/hibernate/jpa/test/query/NullParameterQueryTest.java

@@ -0,0 +1,64 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.jpa.test.query;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+
+import org.hibernate.jpa.test.BaseEntityManagerFunctionalTestCase;
+
+import org.hibernate.testing.TestForIssue;
+import org.junit.Test;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
+import static org.junit.Assert.assertNotNull;
+
+/**
+ * @author Vlad Mihalcea
+ * @see <a href="https://hibernate.atlassian.net/browse/JPA-31">JPA-31</a>
+ */
+@TestForIssue(jiraKey = "JPA-31")
+public class NullParameterQueryTest extends BaseEntityManagerFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class<?>[] {
+				Event.class
+		};
+	}
+
+	@Test
+	public void test() {
+		doInJPA( this::entityManagerFactory, entityManager -> {
+			Event event = new Event();
+
+			entityManager.persist( event );
+		} );
+
+		doInJPA( this::entityManagerFactory, entityManager -> {
+			Event event = entityManager.createQuery(
+					"select e " +
+							"from Event e " +
+							"where (:name is null or e.name = :name)", Event.class )
+					.setParameter( "name", null )
+					.getSingleResult();
+
+			assertNotNull( event );
+		} );
+	}
+
+	@Entity(name = "Event")
+	public static class Event {
+
+		@Id
+		@GeneratedValue
+		private Long id;
+
+		private String name;
+	}
+}