hx-disabled-elt causes unhandled exception when targets not found

Hi there,

Following along with the example of settings for `hx-disabled-elt`, and taking advantage of the inheritance, when the elements specified in the `hx-disabled-elt` are not found htmx fails with `Uncaught TypeError: Cannot read properties of null (reading 'htmx-internal-data')`.

After a fair bit of debugging, the issue comes from a setup like this:
```

In the above example, the elements in the form are disabled and work great, when when the second link it pressed, because there are no child elements of `input` or `button` for find to work on, the uncaught exception is generated.

When the elements specified in a `hx-disabled-elt` are not found (or not children exist) the failure should be more graceful, especially since as an inheritable property it may be used in a number of different circumstances.

This is occurring with htmx 2.0.2.