[Key Vault] Added null checks for HttpResponseException.getResponse()

[vcolin7]

Description

Fixes: #47647

Adds null checks for calls to HttpResponseException.getResponse() in Key Vault clients for better diagnosability.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Copilot]

Pull request overview

This pull request fixes a NullPointerException that occurs when HttpResponseException.getResponse() returns null, which previously caused the real exception (such as authentication errors) to be hidden behind an NPE. The fix adds null checks before accessing the status code from HTTP responses across multiple Key Vault client libraries.

Changes:

• Added null checks for HttpResponseException.getResponse() in exception mapping methods and polling operations
• Ensures that when the response is null, the original exception is returned unchanged or appropriate fallback behavior is applied
• Affects secrets, keys, certificates, and administration client libraries

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
SecretClient.java	Added null checks in delete and recover polling operations before checking 404 status
SecretAsyncClient.java	Added null checks in exception mappers (set, get, restore) and polling operations
CryptographyUtils.java	Added null check in isThrowableRetryable with early return false when response is null
CryptographyClientImpl.java	Added null check in error mapping for get key operation
KeyClient.java	Added null checks in delete and recover polling operations before checking 404 status
KeyAsyncClient.java	Added null checks in exception mappers (create, get, restore) and polling operations
CertificateClient.java	Added null checks in delete and recover polling operations before checking 404 status
CertificateAsyncClient.java	Added null checks in multiple exception mappers and polling operations
KeyVaultAdministrationUtil.java	Added null check in swallowExceptionForStatusCodeSync utility method