Add default value for useRef calls in .tsx files

[matthiasweiss]

This fixes missing default values for useRef calls that use generics, in this case HTMLInputElement.

Currently the returned value is inferred as HTMLInputElement | null | undefined. Adding null as a default value is better, since the returned value is inferred as HTMLInputElement | null due to the signature function useRef<T>(initialValue: T | null): RefObject<T>;.

I ran into this issue because I swapped the <TextInput /> in the <UpdatePasswordForm /> component with a different input component (https://ui.shadcn.com/docs/components/input), which caused an error when passing the ref down to the new component. Adding null as the default value fixed that issue.

[jessarcher]

Looks good to me. The React docs demonstrate passing an initial value of null in this scenario too.

https://react.dev/reference/react/useRef#manipulating-the-dom-with-a-ref