Fix ShareInertiaData middleware for Eloquent strict mode when 2FA is disabled

[onlime]

When we don't want to have 2FA Fortify feature Features::twoFactorAuthentication() enabled, we usually don't have any two_factor_* (namely two_factor_secret) columns on our User model / in our migration. In that case, we couldn't enable Eloquent Strictness, which is recommended for non-production environments. Enabled Model::preventSilentlyDiscardingAttributes() would throw the following MissingAttributeException exception:

The attribute [two_factor_secret] either does not exist or was not retrieved for model [App\Models\User].

This happens on Http/Middleware/ShareInertiaData.php#L57 when trying to access the non-existing attribute:

'two_factor_enabled' => ! is_null($user->two_factor_secret),

This is a simple fix by adding an additional check if the 2FA feature is enabled.