Dashboard error when viewing dockerconfigjson secret with "auth" encoded credentials instead of "username" and "password" keys

[km-bh]

Setup

• Rancher version: 2.7.6
• Rancher UI Extensions: None
• Browser type & version: Chrome (latest) & Firefox (latest)

Describe the bug
When attempting to view a dockerconfigjson-type secret whose data contains "auths.SOME-REGISTRY: {auth:base64-encoded-string}" instead of "auths.SOME-REGISTRY: {username:USER,password:PASS}", the client experiences an error page with the last of the following javascript errors from the console:

console.js:31 Cannot read properties of null (reading 'length')
console.js:31 Cannot read properties of null (reading 'slice')
console.js:31 Cannot read properties of null (reading 'length')
console.js:31 Cannot read properties of null (reading 'slice')

To Reproduce

• base64-encode a username:password string

echo -n 'tester:testing' | base64
dGVzdGVyOnRlc3Rpbmc=

• Create a docker config.json with the previous auth string.

cat <<EOF > config.json
{
    "auths": {
        "testreg.example.org": {
            "auth": "dGVzdGVyOnRlc3Rpbmc="
        }
    }
}
EOF

• Create a dockerconfigjson-type secret from this config.json file

kubectl create secret generic testreg-pull-creds --from-file=.dockerconfigjson=./config.json --type=kubernetes.io/dockerconfigjson

Result
When attempting to view the secret in the Rancher UI (by clicking the name; not viewing as YAML or anything), there is a short pause and the user gets a white screen with "Cannot read properties of null (reading 'slice')". The console shows additional "null" errors.

Expected Result
The user should be presented with a screen showing details of the secret, including values if the option to view secret data is enabled.

Screenshots

Additional context
This error does not seem to be present in 2.8.2. However, only the registry url is shown; it does not attempt to decode the "auth" block to extract the username:password string.