Fix last layer generation for text-only models (microsoft#1513)

Models such as Gemma3 1B which is not a multimodal model will not
generate correct last layer since it's immediately trying to fetch the
model params which it should not. Instead it should only retrieve the
base_model param.

Author: nenad1002

src/python/py/models/builder.py

@@ -2615,8 +2615,12 @@ def has_final_norm(self, module, orig_model):
             # differ.
             model = orig_model.language_model
         elif hasattr(orig_model, "base_model") and hasattr(orig_model.base_model, "model"):
-            # Model is from PEFT
-            model = orig_model.base_model.model
+            if hasattr(orig_model.base_model.model, "model"):
+                # Model is from PEFT
+                model = orig_model.base_model.model
+            else:
+                # Model is text-based only.
+                model = orig_model.base_model
         else:
             model = orig_model