Avoid NoneType on providers pool updates

libs/subliminal_patch/core.py

@@ -105,10 +105,12 @@ class SZProviderPool(ProviderPool):
         # Check if the pool was initialized enough hours ago
         self._check_lifetime()
 
+        providers = set(providers or [])
+
         # Check if any new provider has been added
-        updated = set(providers) != self.providers or ban_list != self.ban_list
-        removed_providers = list(sorted(self.providers - set(providers)))
-        new_providers = list(sorted(set(providers) - self.providers))
+        updated = providers != self.providers or ban_list != self.ban_list
+        removed_providers = list(sorted(self.providers - providers))
+        new_providers = list(sorted(providers - self.providers))
 
         # Terminate and delete removed providers from instance
         for removed in removed_providers:
@@ -128,8 +130,6 @@ class SZProviderPool(ProviderPool):
             self.providers.difference_update(removed_providers)
             self.providers.update(list(providers))
 
-        self.blacklist = blacklist
-
         # Restart providers with new configs
         for key, val in provider_configs.items():
             # Don't restart providers that are not enabled
@@ -154,6 +154,9 @@ class SZProviderPool(ProviderPool):
 
         self.provider_configs = provider_configs
 
+        self.blacklist = blacklist or []
+        self.ban_list = ban_list or {'must_contain': [], 'must_not_contain': []}
+
         return updated
 
     def _check_lifetime(self):