pickle `load_build` function checks if `state` is None, not False

Bug report

Bug description:

Inside of the load_build() function for pickle's BUILD opcode, the C accelerator at one point checks if state is Py_None, while the Python version only checks if state.

https://github.com/python/cpython/blob/34ded1a1a10204635cad27830fcbee2f8547e8ed/Modules/_pickle.c#L6638

https://github.com/python/cpython/blob/34ded1a1a10204635cad27830fcbee2f8547e8ed/Lib/pickle.py#L1765

This means if state is something like an empty dictionary or tuple, the code block under the if statement WILL be run in _pickle.c, but NOT in pickle.py.

As an example, the bytestream b']]b.' has the following disassembly:

    0: ]    EMPTY_LIST
    1: ]    EMPTY_LIST
    2: b    BUILD
    3: .    STOP
highest protocol among opcodes = 1

This will do nothing in pickle.py but error out in _pickle.c with the message state is not a dictionary. The easy solution is to change if state to if state != None, and it shouldn't break any existing functionality. I've attached a pull request.

CPython versions tested on:

3.11

Operating systems tested on:

Linux

Linked PRs

• gh-128966

Compare the BUILD handling in Lib/pickle.py and Modules/_pickle.c, starting with the supplied b']]b.' byte stream and its disassembly. Reproduce the differing behavior and check the existing pickle test coverage; done means both implementations handle false-y state values consistently without the reported error.