When helix/rev2 was using split_common, it didn't work properly and I couldn't type on the right hand side.
The cause is that the following code, added in 0.16.0 to `quantum/keyboard.c`, does not include `quantum/split_common/split_util.h` but instead includes `keyboards/helix/rev2/split_util.h`. Therefore, `split_pre_init()/split_post_init()` in `quantum/split_common/split_util.c` was not called.
```c
#ifdef SPLIT_KEYBOARD
# include "split_util.h"
#endif
```
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