Stubgen crashes on TypeVarTuple usage

[KapJI]

Crash Report

It crashes on Generic[*_Ts].

Traceback

Traceback (most recent call last):
  File "bin/stubgen", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "mypy/stubgen.py", line 1868, in main
  File "mypy/stubgen.py", line 1675, in generate_stubs
  File "mypy/stubgen.py", line 1645, in generate_stub_for_py_module
  File "mypy/nodes.py", line 369, in accept
  File "mypy/stubgen.py", line 441, in visit_mypy_file
  File "mypy/traverser.py", line 115, in visit_mypy_file
  File "mypy/nodes.py", line 1142, in accept
  File "mypy/stubgen.py", line 716, in visit_class_def
  File "mypy/stubgen.py", line 760, in get_base_types
  File "mypy/nodes.py", line 1963, in accept
  File "mypy/stubgen.py", line 310, in visit_index_expr
  File "mypy/nodes.py", line 2269, in accept
  File "mypy/stubgen.py", line 316, in visit_tuple_expr
TypeError: str object expected; got None

To Reproduce

from typing import Generic, TypeVarTuple

_Ts = TypeVarTuple("_Ts")

class ClassName(Generic[*_Ts]):
    pass

Your Environment

• Mypy version used: 1.8.0
• Mypy command-line flags: stubgen test.py
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.12.0
• Operating system and version: macOS 14.3