Comment 12 for bug 1681439

We found a reproducer during fuzzing:

```
qemu-system-x86_64: hw/ide/core.c:724: ide_cancel_dma_sync: Assertion `s->bus->dma->aiocb == NULL' failed.
```

To reproduce run the QEMU with the following command line:
```
qemu-system-x86_64 -cdrom hypertrash.iso -nographic -m 100 -enable-kvm -net none -hda hda.img
```

QEMU Version:
```
# qemu-5.0.0
$ ./configure --target-list=x86_64-softmmu --enable-sanitizers; make
$ x86_64-softmmu/qemu-system-x86_64 --version
QEMU emulator version 5.0.0
Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers
```

To create disk image run:
```
qemu-img create hda.img 10M
```