Update app.py

app.py

@@ -85,7 +85,7 @@ async def infer(model_str, prompt, nprompt="", height=0, width=0, steps=0, cfg=0
         with lock:
             # png_path = "img.png"
             global loopcounter 
-            png_path = get_current_time() + "_" + loopcounter + ".png"
+            png_path = get_current_time() + "_" + str(loopcounter) + ".png"
             loopcounter += 1
             image = save_image(result, png_path, model_str, prompt, nprompt, height, width, steps, cfg, seed)
         return image