CODEC-313: Add unit test

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

Author: arthurscchan

src/test/java/org/apache/commons/codec/net/QuotedPrintableCodecTest.java

@@ -227,6 +227,12 @@ public void testSoftLineBreakEncode() throws Exception {
         assertEquals(qpdata, qpcodec.encode(decoded));
     }
 
+    @Test
+    public void testTooShortByteArray() throws Exception{
+        final QuotedPrintableCodec qpcodec = new QuotedPrintableCodec(true);
+        assertNull(qpcodec.encode("AA"), "Result should be null.");
+    }
+
     @Test
     public void testTrailingSpecial() throws Exception {
         final QuotedPrintableCodec qpcodec = new QuotedPrintableCodec(true);