disable negative prompt when None

app.py

@@ -12,22 +12,25 @@ inference = DiffusionInference()
 controlnet = ControlNetPipeline()
 
 def text_to_image_fn(prompt, model, negative_prompt=None, guidance_scale=7.5, num_inference_steps=50):
-    """
-    Handle text to image generation request
-    """
     try:
         # Model validation - fallback to default if empty
         if not model or model.strip() == '':
             model = config.DEFAULT_TEXT2IMG_MODEL
             
-        # Call the inference module
-        image = inference.text_to_image(
-            prompt=prompt,
-            model_name=model,
-            negative_prompt=negative_prompt,
-            guidance_scale=guidance_scale,
-            num_inference_steps=num_inference_steps
-        )
+        # Create kwargs dictionary for parameters
+        kwargs = {
+            "prompt": prompt,
+            "model_name": model,
+            "guidance_scale": guidance_scale,
+            "num_inference_steps": num_inference_steps
+        }
+        
+        # Only add negative_prompt if it's not None
+        if negative_prompt is not None:
+            kwargs["negative_prompt"] = negative_prompt
+            
+        # Call the inference module with unpacked kwargs
+        image = inference.text_to_image(**kwargs)
         
         if image is None:
             return None, "No image was generated. Check the model and parameters."