Add missing test

Author: garydgregory

src/test/java/org/apache/commons/cli/TypeHandlerTest.java

@@ -210,6 +210,11 @@ public void testCreateFile() {
         assertEquals(file, TypeHandler.createFile(file.toString()));
     }
 
+    @Test
+    public void testCreateFiles() {
+        assertThrows(UnsupportedOperationException.class, () -> TypeHandler.createFiles(null));
+    }
+
     @Test
     public void testCreateURL() throws ParseException, MalformedURLException {
         final URL file = Paths.get("").toAbsolutePath().toUri().toURL();