Getting putMachineConfigurationNoContent when I use --disable-hyperthreading

My command:
```
./firectl \
--kernel=hello-vmlinux.bin \
--root-drive=hello-rootfs.ext4 \
--ncpus=8 \
--memory=50000 \
--tap-device=tap0/AA:FC:00:00:00:01
```
runs fine but when I disable hyperthreading with:
```
./firectl \
--kernel=hello-vmlinux.bin \
--root-drive=rootfs.ext4 \
--ncpus=8 \
--memory=50000 \
--tap-device=tap0/AA:FC:00:00:00:01 \
-t
```
I get this error:

```
INFO[0000] Called startVMM(), setting up a VMM on /home/jayavanth/.firecracker.sock-16505-81
INFO[0000] VMM logging and metrics disabled.
2020-07-27T22:10:58.602820013 [anonymous-instance:ERROR:src/api_server/src/lib.rs:225] Missing mandatory fields.
ERRO[0000] PutMachineConfiguration returned [PUT /machine-config][204] putMachineConfigurationNoContent
WARN[0000] Failed handler "fcinit.CreateMachine": [PUT /machine-config][400] putMachineConfigurationBadRequest &{FaultMessage:Missing mandatory fields.}
FATA[0000] Failed to start machine: [PUT /machine-config][400] putMachineConfigurationBadRequest &{FaultMessage:Missing mandatory fields.}
```

Debug Output: https://pastebin.com/hYDcTHvN