Fix device share plugins npe

[coldzerofear]

There is an NPE issue with the device share plugin， #3241 Not really solving the problem

unit testing

func TestDevices(t *testing.T) {
	others := make(map[string]interface{})
	nodeDevices := vgpu.DecodeNodeDevices("k8s01", "GPU-c496852d-f5df-316c-e2d5-86f0b322ec4c,20,30720,100,NVIDIA-NVIDIA GeForce RTX 3080 Ti,0,false:")
	others["gpu1"] = nodeDevices
	var dev2 *vgpu.GPUDevices = nil
	others["gpu2"] = dev2
	var dev3 Devices = nil
	others["gpu3"] = dev3
	var dev4 Devices = dev2
	others["gpu4"] = dev4
	for key, val := range others {
		if dev, ok := val.(Devices); ok {
			if dev == nil {
				fmt.Println(key, "is nil")
				continue
			}
			fmt.Println(key, "is not nil")
		} else {
			fmt.Println(key, "is not devices")
		}
	}
}

Output results

=== RUN   TestDevices
gpu1 is not nil
gpu2 is not nil
gpu3 is not devices
gpu4 is not nil
--- PASS: TestDevices (0.00s)

This does not meet expectations

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[coldzerofear]

/assign @k82cn

[lowang-bh]

/ok-to-test

[lowang-bh]

please squash commits to one commit.

[Monokaix]

Hi, please sign off your commit with git commit -s

[volcano-sh-bot]

@coldzerofear: PR needs rebase.

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[Monokaix]

Hi，please make ci happy, it's a serious bug and is urgent because we will release new version soon, if you're not availiable we can cherry-pick your commit and submit a new pr: )