Give biased_logits the same dtype as logits

Exllama generates logits in torch Half-dtype, but Outlines requires the
Float-dtype.

This small change converts the logits to the required dtype (whatever
that might be), solving issue #583.

Tested with Exllama on the example code on the github front page, and
#583 is resolved.

outlines/generate/generator.py

@@ -282,7 +282,7 @@ def bias_logits(logits: torch.Tensor, allowed_token_ids: List) -> torch.Tensor:
     A view of the original logits tensor where some values are masked.
 
     """
-    biased_logits = torch.full(logits.shape, -math.inf, device=logits.device)
+    biased_logits = torch.full_like(logits, -math.inf, device=logits.device)
     for i, ids in enumerate(allowed_token_ids):
         biased_logits[i, ids] = logits[i, ids]
     return biased_logits