PCP-3797: Added nil pointer check before dereferencing Nodegroup version

[VivekPratapSingh1334]

Added a check to ensure that the nodegroup version is not nil before dereferencing it.

What type of PR is this?

/kind bug

What this PR does / why we need it:

This PR adds a nil pointer check for the nodegroup version in the reconcileNodegroupVersion function. This prevents potential runtime panics caused by dereferencing a nil pointer when the nodegroup version is not set during AWSManagedMachinePool reconciliation .

Example: When the nodegroup status in in "CREATE_FAILED" state due to unsupported AWS Launch template in Palette then the nodegroup version is nil and we encounter panic calls.

Which issue(s) this PR fixes:
Fixes https://spectrocloud.atlassian.net/browse/PCP-3797

Upstream fix : kubernetes-sigs#5019

[spectro-prow]

@VivekPratapSingh1334: The label(s) kind/bug cannot be applied, because the repository doesn't have them

In response to this:

Added a check to ensure that the nodegroup version is not nil before dereferencing it.

What type of PR is this?

/kind bug

What this PR does / why we need it:

This PR adds a nil pointer check for the nodegroup version in the reconcileNodegroupVersion function. This prevents potential runtime panics caused by dereferencing a nil pointer when the nodegroup version is not set during AWSManagedMachinePool reconciliation .

Example: When the nodegroup status in in "CREATE_FAILED" state due to unsupported AWS Launch template in Palette then the nodegroup version is nil and we encounter panic calls.

Which issue(s) this PR fixes:
Fixes https://spectrocloud.atlassian.net/browse/PCP-3797

Upstream fix : kubernetes-sigs#5019

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[spectro-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: AmitSahastra, pavansokkenagaraj, VivekPratapSingh1334
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