Don't scope by removed tenant

[krydos]

Hi,
thanks for keeping this package maintained. You saved lots of time for us and our project.

We've got one issue though. In our project we use applyTenantScopesToDeferredModels() method at the beginning of the app life circle. Then somewhere in the middle of that life circle we call \Landlord::removeTenant('tenant_id') which means we don't want to scope by a tenant_id for all the models we're going to use after the removeTenant call. But instead of not scoping we're getting exception saying that $tenant must be a string key or an instance of \Illuminate\Database\Eloquent\Model. It's all because tenant_id isn't available in tenants property of TenantManager class anymore but the scope was created already and it expects that tenant_id available.

This pull request fixes the issue. Let me know if the issue description isn't clear or the fix has other issues I didn't notice.

Thanks

[krydos]

Seems like I maybe should update applyTenantScopes as well

[krydos]

CC @nunomazer