fix: panic when allow-empty-cloud-config is set

[andyzhangx]

What type of PR is this?
/kind bug

What this PR does / why we need it:
fix: panic when allow-empty-cloud-config is set

Which issue(s) this PR fixes:

Fixes #1696

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Special notes for your reviewer:

Release note:

fix: panic when allow-empty-cloud-config is set

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx

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[andyzhangx]

/retest

[andyzhangx]

/retest

[andyzhangx]

/retest

[andyzhangx]

/retest

[andyzhangx]

/retest

[k8s-ci-robot]

@andyzhangx: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-azuredisk-csi-driver-e2e-capz-windows-2019	811840a	link	true	/test pull-azuredisk-csi-driver-e2e-capz-windows-2019

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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