Address compiler warnings.

Author: Gary Gregory

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

@@ -474,7 +474,7 @@ public void testFormatThrowsNullPointerException() {
         final CSVFormat cSVFormat = CSVFormat.MYSQL;
 
         try {
-            cSVFormat.format(null);
+            cSVFormat.format((Object[]) null);
             fail("Expecting exception: NullPointerException");
         } catch(final NullPointerException e) {
             assertEquals(CSVFormat.class.getName(), e.getStackTrace()[0].getClassName());
@@ -639,7 +639,6 @@ public void testSerialization() throws Exception {
     @Test
     public void testToString() {
 
-        final CSVFormat cSVFormat = CSVFormat.POSTGRESQL_TEXT;
         final String string = CSVFormat.INFORMIX_UNLOAD.toString();
 
         assertEquals("Delimiter=<|> Escape=<\\> QuoteChar=<\"> RecordSeparator=<\n> EmptyLines:ignored SkipHeaderRecord:false", string);