Make sure componentRef types match base component type

[Markionium]

Pull request checklist

• Addresses an existing issue: Fixes #0000
• Include a change request file using $ npm run change

Description of changes

BaseComponent defines the componentRef as receiving null as a possible value.

componentRef?: (ref: T | null) => (void | T);

However a lot of the components defined the prop without taking the null value into account. But do not guarantee that this is actually the case in the component. This caused a hole in the type system as the function can be called with null but we don't protect against it.

componentRef?: (component: ICommandBar) => void;

This PR fixes up all the componentRef type definitions by adding the possible null value.

componentRef?: (component: ICommandBar | null) => void;

Focus areas to test

Effects types only, so should not have any effect on JS.

[jordandrako]

@Jahnp Can you manually approve/merge this? npm start is borked at the moment and this will should fix it.

[Jahnp]

@jordandrako, it looks good to me, but with a change this wide-ranging, @dzearing should really be the one to merge.