updated test

Author: hmottestad

core/sail/memory/src/test/java/org/eclipse/rdf4j/sail/memory/MemoryStoreMinusScopingDebugTest.java

@@ -13,6 +13,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 import java.io.IOException;
 import java.io.StringReader;
@@ -117,6 +118,22 @@ public void testSES2250BindErrors() {
 		}
 	}
 
+	@Test
+	public void testEmptyUnion() {
+		try (SailRepositoryConnection conn = repository.getConnection()) {
+
+			String query = "PREFIX : <http://example.org/> "
+					+ "SELECT ?visibility WHERE {"
+					+ "OPTIONAL { SELECT ?var WHERE { :s a :MyType . BIND (:s as ?var ) .} } ."
+					+ "BIND (IF(BOUND(?var), 'VISIBLE', 'HIDDEN') as ?visibility)"
+					+ "}";
+			try (TupleQueryResult result = conn.prepareTupleQuery(QueryLanguage.SPARQL, query).evaluate()) {
+				assertNotNull(result);
+				assertFalse(result.hasNext());
+			}
+		}
+	}
+
 	private List<BindingSet> selectWithData(RepositoryConnection conn, String data, RDFFormat format, String body)
 			throws IOException {
 		String sparql = PREFIX + body;