Fixed invalid pipeline_class_name parameter. (huggingface#4590)

* Fixed invalid pipeline_class_name parameter.

* Fix the format

Author: aihao2000

scripts/convert_original_stable_diffusion_to_diffusers.py

@@ -147,6 +147,7 @@
     if args.pipeline_class_name is not None:
         library = importlib.import_module("diffusers")
         class_obj = getattr(library, args.pipeline_class_name)
+        pipeline_class = class_obj
     else:
         pipeline_class = None