Fix torch_dtype warning showing wrong value in from_single_file

The warning message intended to show the invalid torch_dtype value passed
by the user, but the variable was already reassigned to torch.float32
before the warning was logged. Move the reassignment after the warning
so the message correctly displays the original invalid value.

Author: Ricardo-M-L

src/diffusers/loaders/single_file.py

@@ -366,10 +366,10 @@ def from_single_file(cls, pretrained_model_link_or_path, **kwargs) -> Self:
         is_legacy_loading = False
 
         if torch_dtype is not None and not isinstance(torch_dtype, torch.dtype):
-            torch_dtype = torch.float32
             logger.warning(
                 f"Passed `torch_dtype` {torch_dtype} is not a `torch.dtype`. Defaulting to `torch.float32`."
             )
+            torch_dtype = torch.float32
 
         # We shouldn't allow configuring individual models components through a Pipeline creation method
         # These model kwargs should be deprecated