mthd_my_read_query_result segment fault at parsing session_track_info

SESSION_TRACK_STATE_CHANGE should be treated differently from other trackers
https://mariadb.com/kb/en/library/mysql_session_track_get_first/
SESSION_TRACK_STATE_CHANGE:
length encode int: "1" (changed) or "0" (unchanged).
int<1> : boolean info;
SESSION_TRACK_SYSTEM_VARIABLES:
length encode int: length;
length encode string: key;
length encode string: value;

attach with my candidate fix