According to the C standard the free(void *ptr) function: if ptr is a null
pointer, no action occurs.
Signed-off-by: Peter Züger <zueger.peter@icloud.com>
To use it a board should define MICROPY_PY_USSL=1 and MICROPY_SSL_MBEDTLS=1
at the Makefile level. With the provided configuration it adds about 64k
to the build.