Add missing tests

Author: garydgregory

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

@@ -183,6 +183,8 @@ private CSVPrinter printWithHeaderComments(final StringWriter sw, final Date now
         // Use withHeaderComments first to test CSV-145
         // @formatter:off
         final CSVFormat format = baseFormat.builder()
+                .setHeaderComments((String[]) null) // don't blow up
+                .setHeaderComments((Object[]) null) // don't blow up
                 .setHeaderComments("Generated by Apache Commons CSV 1.1", now)
                 .setCommentMarker('#')
                 .setHeader("Col1", "Col2")
@@ -500,6 +502,15 @@ public void testEolQuoted() throws IOException {
         }
     }
 
+    @SuppressWarnings("unlikely-arg-type")
+    @Test
+    public void testEquals() throws IOException {
+        // Don't use assertNotEquals here
+        assertFalse(CSVFormat.DEFAULT.equals(null));
+        // Don't use assertNotEquals here
+        assertFalse(CSVFormat.DEFAULT.equals(""));
+    }
+
     @Test
     public void testEscapeBackslash1() throws IOException {
         final StringWriter sw = new StringWriter();