Voiding an encounter "deletes" the provider and the encounter cannot be unvoided

When an encounter is voided (either from Manage Encounters or deleting from an HTML form on the dashboard), and you go to Manage Encounters and search for that encounter, you find there are no providers listed under the Providers section. If you try to unvoid the encounter, it can't because there are now providers. It says...

Please fix all errors and try again.
At least one provider is required