[automerger] [DO NOT MERGE] AMR WB encoder: prevent OOB write in ACELP_4t64_fx am: 04e48ed870 am: 8b8f583fa5 am: 30d710f5af am: 3faebc5eb3

Change-Id: Ie343878173439dd512a05cb72fae6e0caa2d6056