Fix None model_id handling in Gradio examples

- Add None check in estimate_model_size()
- Add None check in should_quantize()
- Add ValueError for None/empty model_id in load_model()
- Add validation in gradio_chat() with user-friendly message

app.py

@@ -404,6 +404,11 @@ def gradio_chat(
     max_tokens: int,
 ):
     """Gradio chat interface handler."""
+    # Validate model_id
+    if not model_id:
+        yield "Please select a model first."
+        return
+
     # Build messages from history
     messages = []
     for user_msg, assistant_msg in history:

config.py

@@ -122,6 +122,9 @@ def estimate_model_size(model_id: str) -> Optional[int]:
 
     Returns None if size cannot be determined.
     """
+    if model_id is None:
+        return None
+
     # Check known models first
     if model_id in MODEL_SIZE_ESTIMATES:
         return MODEL_SIZE_ESTIMATES[model_id]
@@ -141,6 +144,9 @@ def should_quantize(model_id: str) -> str:
 
     Returns: "none", "int8", or "int4"
     """
+    if model_id is None:
+        return "none"
+
     if config.default_quantization != "none":
         return config.default_quantization
 

models.py

@@ -84,9 +84,15 @@ def load_model(
 
     Returns:
         LoadedModel with model and tokenizer ready for inference
+
+    Raises:
+        ValueError: If model_id is None or empty
     """
     global _current_model
 
+    if not model_id:
+        raise ValueError("model_id cannot be None or empty")
+
     # Check if already loaded
     if not force_reload and _current_model is not None:
         if _current_model.model_id == model_id: