Strange OK packet with trailing garbage

Update: This can be reproduced with:

CREATE DATABASE foobar CHARACTER SET utf16;

USE foobar

This seems to happen sometimes when a query is being sent right before a USE db command is executed. Here's the hexdumpped OK packet that shows the odd trailing garbage:

0000  1f 00 00 01 00 00 00 02  40 00 00 00 00 15 01 13   ········ @·······

0010  12 66 72 61 75 64 5f 72  69 73 6b 5f 73 63 6f 72   ·fraud_r isk_scor

0020  69 6e 67                                           ing

Note that there's an extra 0x00 byte at an offset of 14 after which is the 0x15 byte that appears to be the real session tracking length. Technically this is correct as the variable tracker length is set to zero but it's surprising that there's "garbage" data after it in the OK packet.