fix: invalid memory address

[ShaPoHun]

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What type of this PR

Examples of user facing changes:

• Bug fixes
  "invalid memory address or nil pointer dereference" in vpc_nat.go

Which issue(s) this PR fixes:

Fixes #(issue-number)
#2583

[github-actions]

• The commit messages for both patches are not informative enough. They only mention "fix: invalid memory address" without any further explanation of what the issue was and how it was fixed. It would be better to provide more details in the commit messages.
• In the first patch, there is a potential bug if the "image" key does not exist in the ConfigMap data. In that case, the code will still try to assign an empty string to the vpcNatImage variable, which could cause unexpected behavior later on. It would be better to return early from the function if the "image" key is not found.
• In the second patch, there is a missing check for the "IsNotFound" error. If the error is "IsNotFound", the function should return early instead of logging an error message.

[github-actions]

• The commit message should be more descriptive and informative. It should explain what the patch does and why it is necessary.
• In the first patch, there is a potential bug in the resyncVpcNatConfig() function. If the "image" key is not found in the ConfigMap data, the vpcNatImage variable will still be set to an empty string, which could cause issues later on. A better approach would be to return an error or use a default value if the key is not found.
• In the second patch, there is a potential bug in the resyncVpcNatConfig() function. If the error returned by the ConfigMaps() method is "not found", the function returns without doing anything. However, this could cause issues if the ConfigMap is created later on. A better approach would be to log a warning message and continue with the function.