Model: Fix max_seq_len fallbacks

The rope alpha calculation caused an error if max seq len isn't
provided. This is because the model's max sequence length was not
stored as the target for alpha calculation.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

backends/exllamav2/model.py

@@ -237,7 +237,8 @@ class ExllamaV2Container(BaseModelContainer):
         base_seq_len = self.config.max_seq_len
 
         # Set the target seq len if present
-        target_seq_len = kwargs.get("max_seq_len")
+        # Fallback to base_seq_len if not provided
+        target_seq_len = unwrap(kwargs.get("max_seq_len"), base_seq_len)
 
         # Set the rope scale
         self.config.scale_pos_emb = unwrap(