fix web-ui (#3822)

Author: Jintao-Huang

swift/llm/argument/base_args/template_args.py

@@ -33,7 +33,7 @@ class TemplateArguments:
     system: Optional[str] = None  # Override the default_system in the template.
     max_length: Optional[int] = None
 
-    truncation_strategy: Optional[Literal['delete', 'left', 'right']] = None
+    truncation_strategy: Literal['delete', 'left', 'right', None] = None
     max_pixels: Optional[int] = None
     tools_prompt: str = 'react_en'  # Override the default_tools_prompt in the template.
     norm_bbox: Literal['norm1000', 'none', None] = None

swift/llm/argument/rlhf_args.py

@@ -56,7 +56,7 @@ class GRPOArguments(GRPOArgumentsMixin):
     # multi step
     num_iterations: int = 1
 
-    truncation_strategy: Optional[Literal['delete', 'left', 'right']] = None
+    truncation_strategy: Literal['delete', 'left', 'right', None] = None
 
 
 @dataclass