oss-fuzz: SEGV on unknown address 0x6330001744ff

reproduce with ./build-asan/tests/dav1d_fuzzer clusterfuzz-testcase-minimized-dav1d_fuzzer-5727148069879808

clusterfuzz-testcase-minimized-dav1d_fuzzer-5727148069879808

ASAN:DEADLYSIGNAL
=================================================================
==16447==ERROR: AddressSanitizer: SEGV on unknown address 0x6330001744ff (pc 0x7f4df15454cc bp 0x000000000000 sp 0x7ffdb2da26c0 T0)
==16447==The signal is caused by a READ memory access.
    #0 0x7f4df15454cb in derive_warpmv ../src/decode.c:311
    #1 0x7f4df15624a2 in decode_b ../src/decode.c:1676
    #2 0x7f4df156755a in decode_sb ../src/decode.c:1884
    #3 0x7f4df1568944 in dav1d_decode_tile_sbrow ../src/decode.c:2319
    #4 0x7f4df156d53e in dav1d_decode_frame ../src/decode.c:2664
    #5 0x7f4df1571157 in dav1d_submit_frame ../src/decode.c:3036
    #6 0x7f4df153c8cd in dav1d_parse_obus ../src/obu.c:1088
    #7 0x7f4df161c2e7 in dav1d_decode ../src/lib.c:201
    #8 0x55e17f0a7f6d in LLVMFuzzerTestOneInput ../tests/libfuzzer/dav1d_fuzzer.c:82
    #9 0x55e17f0a773f in main ../tests/libfuzzer/main.c:87
    #10 0x7f4df0f48ae6 in __libc_start_main (/lib64/libc.so.6+0x21ae6)
    #11 0x55e17f0a7969 in _start (/home/janne/src/dav1d/build-asan/tests/dav1d_fuzzer+0x1969)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ../src/decode.c:311 in derive_warpmv
==16447==ABORTING