SDL_GetNumTouchFingers(): 0 is a valid value. negative is automatically an error

include/SDL3/SDL_touch.h

@@ -115,7 +115,7 @@ extern DECLSPEC SDL_TouchDeviceType SDLCALL SDL_GetTouchDeviceType(SDL_TouchID t
  *
  * \param touchID the ID of a touch device
  * \returns the number of active fingers for a given touch device on success
- *          or 0 on failure; call SDL_GetError() for more information.
+ *          or a negative error code on failure; call SDL_GetError() for more information.
  *
  * \since This function is available since SDL 3.0.0.
  *