Update django_mongodb_backend/schema.py

Co-authored-by: Copilot <[email protected]>

Author: aclark4life

django_mongodb_backend/schema.py

@@ -461,7 +461,7 @@ def _get_encrypted_fields_map(self, model, client, create_data_keys=False):
         options = client._options
         auto_encryption_opts = options.auto_encryption_opts
         kms_provider = router.kms_provider(model)
-        master_key = self.connection.settings_dict.get("KMS_CREDENTIALS").get(kms_provider)
+        master_key = self.connection.settings_dict.get("KMS_CREDENTIALS", {}).get(kms_provider)
         client_encryption = ClientEncryption(
             auto_encryption_opts._kms_providers,
             auto_encryption_opts._key_vault_namespace,