Debug build only: C functions that raise Python exceptions must return nullptr

[v-ein]

Version of Dear PyGui

Version: 1.8.0 (a debug version built myself)
Operating System: Windows 10

My Issue/Question

When I was debugging DPG (a debug build, of course), I noticed that sometimes Python hits the same debug assertion in various DPG calls. The following causes it to happen:

• a C function in DPG calls mvThrowPythonError or PyErr_SetStringand, effectively raising a Python exception,
• that function then returns Py_None (typically via GetPyNone()).

Upon returning from a C function, Python expects to get either an exception or a PyObject*, but not both. A function that raised an exception must return NULL.

This issue does not occur in the release version but might substantially hinder the use of the debug build if DPG throws exceptions for some reason (e.g. a missing UUID).

To Reproduce

TBD. I still need to create a minimal example.

Expected behavior

No debug assertions in such cases.

Screenshots/Video

TBD

Standalone, minimal, complete and verifiable example

TBD

[v-ein]

I have a partial fix for this issue, but still need to create an example program that can be used as a test. When fixing the issue, I was using my current project, which can't be used as a minimal example. Will submit the fix a bit later, when I have a chance to upgrade to DPG 1.9.1.