fix: replace mutable default arguments with None

[Mr-Neutr0n]

Summary

Using mutable default arguments (e.g. def f(history=[])) is a well-known Python anti-pattern (docs). The default object is evaluated once at function definition time and shared across all calls, so mutations in one call silently leak into subsequent calls.

This PR replaces every mutable default list with None and initializes a fresh list inside the function body.

Changes

File	Function	Parameter
internvl_chat/internvl/model/internlm2/modeling_internlm2.py	InternLM2ForCausalLM.build_inputs	history=[] -> history=None
internvl_chat/internvl/model/internlm2/modeling_internlm2.py	InternLM2ForCausalLM.chat	history=[] -> history=None
internvl_chat/internvl/model/internlm2/modeling_internlm2.py	InternLM2ForCausalLM.stream_chat	history=[] -> history=None
clip_benchmark/clip_benchmark/datasets/builder.py	build_vtab_dataset	classnames=[] -> classnames=None
internvl_chat/eval/mathvista/utilities.py	contains_quantity_word	special_keep_words=[] -> special_keep_words=None

Example of the bug

def chat(history=[]):
    history.append("new message")
    return history

chat()  # ['new message']
chat()  # ['new message', 'new message']  <-- unexpected!

Test plan

• Verified no remaining =[] or ={} in function signatures across the codebase
• Each guard clause (if x is None: x = []) is placed before the parameter's first use
• No behavioral change for callers that already pass an explicit argument