Remove unnecessary blank line in multi_provider.py

Author: mshsheikh

src/agents/models/multi_provider.py

@@ -151,7 +151,6 @@ def get_model(self, model_name: str | None) -> Model:
         # Defensive validation
         if model_name is None or model_name == "":
             raise UserError("Model name must be provided and non-empty.")
-            
         if prefix and self.provider_map and (provider := self.provider_map.get_provider(prefix)):
             return provider.get_model(model_name)
         else: