api: remove double NULL check

We check if the object is NULL before appending it to the
obj_list and a second time as we append it. Drop the latter
as it makes the code more confusing than it needs to be.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
wflinfo: use waffle_dl_sym to get core functions

Unlike MacOS and Linux, Windows is less fortunate to people who
prefer to fetch core OpenGL symbols via  wglGetProcAddress.

Until we merge piglit's dispatch in one shape or the other, we'll
need to manually pick/set the correct function that is used for
each function.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>