[automerger] Fix overflow/dos in 3gg text description parsing am: 851e22d1dc am: efeff07750 am: 93e7dd1e8b am: 0d6a0e7d88 am: ec9f664d7b am: 806e1cbf2f
am: e44b6c7854

Change-Id: I04fd7f315d04d70aa8a47a2cfde20ab16e8b9826