Unexpected behavior when dealing with stores (createStore)

Hello everyone, so I have this line of code:

{data.user ? <A href={`/years/${data.user.position || "fy"}`}>Begin studying</A> : <A href="/login"><FaBrandsMicrosoft /> Login</A>}

{data.user ? <A href={`/years/${data.user.position || "fy"}`}>Begin studying</A> : <A href="/login"><FaBrandsMicrosoft /> Login</A>}

It works perfectly but when the user logs out (user sets to null), they get this error in the console:

TypeError: Cannot read properties of null (reading 'position')