GetVirtualMachinesMetricID method throwing panic error when accessing VMs from reponse

**Problem**: VirtualMachineService.GetVirtualMachinesMetricID method throws panic when it is trying to access the VMs response from server in below line of code. This happens when the count in the response is 1 but the actual VirtualMachinesMetrics array in the reponse is nil or empty. This is causing panic in the caller [CAPC](https://github.com/kubernetes-sigs/cluster-api-provider-cloudstack/blob/7b87895be9aa7d9dca1e2f70892feafd33ca4e59/pkg/cloud/instance.go#L61)

panic error is happening at: https://github.com/apache/cloudstack-go/blob/main/cloudstack/VirtualMachineService.go#L5543

**error**: `panic: runtime error: index out of range [0] with length 0`

version of cloudstack-go used: `2.16.1`

Please help investigate this error and let us know if this response is not expected