[CSV-121] Exception that the header contains duplicate names when the column names are empty. Add a test that shows that ONE missing header is OK.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/csv/trunk@1602166 13f79535-47bb-0310-9956-ffa450edef68

src/test/java/org/apache/commons/csv/CSVParserTest.java

@@ -633,6 +633,22 @@ public class CSVParserTest {
         assertFalse(records.hasNext());
     }
 
+    @Test
+    public void testHeaderMissing() throws Exception {
+        final Reader in = new StringReader("a,,c\n1,2,3\nx,y,z");
+
+        final Iterator<CSVRecord> records = CSVFormat.DEFAULT.withHeader().parse(in).iterator();
+
+        for (int i = 0; i < 2; i++) {
+            assertTrue(records.hasNext());
+            final CSVRecord record = records.next();
+            assertEquals(record.get(0), record.get("a"));
+            assertEquals(record.get(2), record.get("c"));
+        }
+
+        assertFalse(records.hasNext());
+    }
+
     @Test
     public void testHeaderComment() throws Exception {
         final Reader in = new StringReader("# comment\na,b,c\n1,2,3\nx,y,z");