Fixed [JACKSON-763], problems with convertValue() to List<byte[]>

src/java/org/codehaus/jackson/util/TokenBuffer.java

diff --git a/src/java/org/codehaus/jackson/util/TokenBuffer.java b/src/java/org/codehaus/jackson/util/TokenBuffer.java
index 3c3cfb5..6aa2356 100644
--- a/src/java/org/codehaus/jackson/util/TokenBuffer.java
+++ b/src/java/org/codehaus/jackson/util/TokenBuffer.java
@@ -1079,6 +1079,8 @@
             ByteArrayBuilder builder = _byteBuilder;
             if (builder == null) {
                 _byteBuilder = builder = new ByteArrayBuilder(100);
+            } else {
+                _byteBuilder.reset();
             }
             _decodeBase64(str, builder, b64variant);
             return builder.toByteArray();