avcodec/dirac_dwt_template: Fix Integer overflow in horizontal_compose_dd137i()

Fixes: 5894/clusterfuzz-testcase-minimized-5315325420634112
Fixes: runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg


Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>