Editing a cluster config gives error "Cannot read properties of null (reading 'save')" / "a.config is null"

[osklil]

Setup

• Rancher version: 2.10.1
• Rancher UI Extensions: none
• Browser type & version: Mozilla Firefox 134.0.2 (64-bit)

Describe the bug
Trying to edit cluster config gives the error "a.config is null" (in Firefox) and "Cannot read properties of null (reading 'save')" in Chrome.

To Reproduce

1. Log on to the Rancher web interface.
2. Go Cluster Management (/dashboard/c/_/manager/provisioning.cattle.io.cluster)
3. Click on the ⋮ menu to the right of a cluster, then Edit Config
4. Click Save

Result
The red error "a.config is null" is displayed at top. The "Save" button briefly turns to "Error"

Expected Result
There should be no error.

[osklil]

It turned out to be an empty/partially configured Machine Pool. I deleted it, and now it works. I believe these empty/partial Machine Pool worked with previous versions of Rancher (2.8.5 but not 2.9.3 and later).

[richard-cox]

@osklil can you provide information on the type of cluster and how it was originally created, and the role of the user that was editing the cluster?

[osklil]

The Provider of cluster is VMware vSphere. It was set up from a Local RKE2 cluster. The user role is a Global Administrator.

[osklil]

Here is the scenario. With Rancher 2.6.x or 2.7x, additional machine pools were created. They were scaled down to zero nodes. Then the upgrade to 2.8.x, 2.9.x, and 2.10.x was made.