Regression: objToJSON "nonvoid function does not return a value" error is back
There was an issue in 2013, #5326, where `initObjToJSON` in `pandas/_libs/src/ujson/python/objToJSON.c` was causing a build error due to it lacking a return value.  Specifically, the issue was:

```
pandas/_libs/src/ujson/python/objToJSON.c: In function ‘initObjToJSON’:
pandas/_libs/src/ujson/python/objToJSON.c:181:1: error: control reaches end of non-void function [-Werror=return-type]
```

This was fixed at the time in #5334.  However, a recent commit, #30710, removed the return value again.  This has caused the warning/error to reappear, causing our builds of pandas 1.0.0 to fail.  The warning is appearing in your CI builds as well.  The difference is that we have it configured as an error.

Would it be possible to set a valid return value for the function?  Thank you.