Rerunning fuzzing afresh found the following crash because uint64 len > max(int64)
was cast to int resulting in negative number:

    "\x960000000\xbd"

    panic: bytes.Buffer.Grow: negative count

    goroutine 1 [running]:
    bytes.(*Buffer).Grow(0xc000012140?, 0xc00010abf8?)
            /home/kirr/src/tools/go/go1.22/src/bytes/buffer.go:166 +0xb4
    github.com/kisielk/og-rek.(*Decoder).bufLoadBytesData(0xc000072000, 0xbd30303030303030)
            /home/kirr/src/neo/src/github.com/kisielk/og-rek/ogorek.go:788 +0xd5
    github.com/kisielk/og-rek.(*Decoder).bufLoadBinData8(0xc000072000)
            /home/kirr/src/neo/src/github.com/kisielk/og-rek/ogorek.go:776 +0x105
    github.com/kisielk/og-rek.(*Decoder).loadBytearray8(0xc000072000)
            /home/kirr/src/neo/src/github.com/kisielk/og-rek/ogorek.go:1270 +0x34
    github.com/kisielk/og-rek.(*Decoder).Decode(0xc000072000)
            /home/kirr/src/neo/src/github.com/kisielk/og-rek/ogorek.go:311 +0x1a2c
    github.com/kisielk/og-rek.Fuzz({0x7fd052187000, 0x9, 0x9})
            /home/kirr/src/neo/src/github.com/kisielk/og-rek/fuzz.go:15 +0xf6
    go-fuzz-dep.Main({0xc00010af38, 0x1, 0x5bc338?})
            go-fuzz-dep/main.go:36 +0x14c
    main.main()
            github.com/kisielk/og-rek/go.fuzz.main/main.go:15 +0x35
    exit status 2

-> Fix it by first comparing uint64 len without casting and further casting to
int only after we cap the len to be in safe range.