[automerger] Fix overflow/dos in 3gg text description parsing am: 851e22d1dc am: efeff07750 am: 93e7dd1e8b am: 0d6a0e7d88 am: ec9f664d7b
am: 806e1cbf2f

Change-Id: If8f647ff59b17f9cecae2ca70f289d37a24ff318