added cpu support to img2img.py

scripts/img2img.py

@@ -40,7 +40,8 @@ def load_model_from_config(config, ckpt, verbose=False):
         print("unexpected keys:")
         print(u)
 
-    model.cuda()
+    if torch.cuda.is_available():
+        model.cuda()
     model.eval()
     return model