Fixed octal printing of bytearrays

Change-Id: Ia848d7fae9aeab89e65b00f05cee6c1e6d649d94

java/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java

@@ -249,7 +249,7 @@ public final class MessageNanoPrinter {
             } else if (ch >= 32 && ch < 127) {
                 builder.append((char) ch);
             } else {
-                builder.append(String.format("\\%03o", ch));
+                builder.append(String.format("\\%03o", ch && 0xff));
             }
         }
         builder.append('"');