Fix support for ET repo generated pte by adding batch dim (#1177)

Author: Jack-Khuu

torchchat/model.py

@@ -951,6 +951,11 @@ def forward(self, x, input_pos):
             # the first element to get the tensor
             assert len(logits) == 1
             logits = logits[0]
+
+            # Add a batch dimension, if it's missing (e.g. some pte's
+            # exported from the ExecuTorch repo)
+            if logits.dim() == 2:
+                logits = logits.unsqueeze(0)
             return logits
 
         def setup_caches(self, max_batch_size, max_seq_length):