zero initialize allocated memory

initialize allocated memory if not written after allocation
to prevent invalid indices from being accessed

Bug: 160633884
Test: initialize memory such that only msb is 0,
eg. memset(s->dec_table, 0x7f, size),
run fuzzer with testvector

Change-Id: I0951bb4a898f5ecfe4d4d0c302ad11b3e62b434e
3 files changed