Use sizeof(char) in place for sizeof(void) (#515)
Use sizeof(char) in place for sizeof(void) (#515)

The latter is invalid C++, even though gcc accepts it as an extension

Signed-off-by: Michel Hidalgo <2c7f9fd20fbeb41ce8894ec4653d66fa7f3b6e1a@ekumenlabs.com>
ros2/demos,ros2/demos,ros2/demos,ros2/demos