add hw6 markups

app.py

@@ -99,8 +99,10 @@ def infer(
             }
     
     print("in infer 1")
+    print("controlnet_enable", controlnet_enable)
 
-    if controlnet_enable:
+    controlnet = None
+    if controlnet_enable and control_image is not None:
         print("in controlnet_enable")
         if control_mode == "canny":
             controlnet = ControlNetModel.from_pretrained("lllyasviel/control_v11p_sd15_canny",