fix: unhandled error when AWS config or profile don't exist

[jonscheiding]

Description of changes

If the AWS profile specified in the Amplify config doesn't exist, or if the AWS config files themselves don't exist, various Amplify operations log this error:

🛑 Failed to get profile credentials
Cannot read properties of undefined (reading 'accessKeyId')

Depending on the operation and circumstances, this can be just a spurious message that doesn't interfere with the operation, or it can be an actual error.

Issue #, if available

Description of how you validated changes

• Tested locally with modified version and a missing AWS profile

Checklist

• [x] PR description included
• [x] yarn test passes
• [x] Tests are changed or added
• [x] Relevant documentation is changed or added (and PR referenced)
• [x] New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• [x] Pull request labels are added

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.