Simple select throws some errors due to unmounted ref

[Skaiir]

Describe the Bug

Following this change, sentry is picking up a few errors: Cannot read properties of undefined (reading 'focus' / 'blur')

This looks like it 's trying to call functions on the component when it isn't mounted.

After a bit more investigation, this is a full blown bug as the mousedown event is trying to access the dropdown even when the component is disabled, and hence not rendered.

Steps to Reproduce

1. disable a simpleSelect
2. click around on it
3. an exception it thrown

Expected Behavior

3. no exception should be thrown