Simplify fields to extract calculation

fastapi/dependencies/utils.py

@@ -750,18 +750,14 @@ def request_params_to_args(
     if not fields:
         return values, errors
 
-    fields_to_extract = fields
     default_convert_underscores = True
 
     params_to_process: Dict[str, Any] = {}
 
-    model_fields = [
-        field for field in fields if lenient_issubclass(field.type_, BaseModel)
-    ]
-    if model_fields:
     fields_to_extract = [
         cached_field
-            for field in model_fields
+        for field in fields
+        if lenient_issubclass(field.type_, BaseModel)
         for cached_field in get_cached_model_fields(field.type_)
     ]