ensure enable_input_require_grads is called on model before getting t…

…he peft model (#345)

src/axolotl/utils/models.py

@@ -391,6 +391,8 @@ def load_adapter(model, cfg, adapter):
 
     if adapter is None:
         return model, None
+    if hasattr(model, "enable_input_require_grads"):
+        model.enable_input_require_grads()
     if adapter in ["lora", "qlora"]:
         return load_lora(model, cfg)
     if adapter == "llama-adapter":