fix validation for qlora merge

src/axolotl/utils/validation.py

@@ -1,9 +1,14 @@
 def validate_config(cfg):
     if cfg.adapter == "qlora":
-        assert cfg.load_in_8bit is False
-        assert cfg.load_4bit is False
-        assert cfg.load_in_4bit is True
-    pass
+        if cfg.merge_lora:
+            # can't merge qlora if loaded in 8bit or 4bit
+            assert cfg.load_in_8bit is False
+            assert cfg.load_4bit is False
+            assert cfg.load_in_4bit is False
+        else:
+            assert cfg.load_in_8bit is False
+            assert cfg.load_4bit is False
+            assert cfg.load_in_4bit is True
     # TODO
     # MPT 7b
     # https://github.com/facebookresearch/bitsandbytes/issues/25