Access to not initialized memory in SDL_CreateRenderer opengles/opengles2

Hi,

There is a blatant of some not initialized memory when creating a sdl
renderer of type “opengles”, or “opengles2”. It seems to have no effect on
my devices, but I cannot guarantee that all drivers are robust enough to
this issue.

https://bugzilla.libsdl.org/show_bug.cgi?id=3355

It would be nice if someone with good understanding or the SDL_Render and
opengles could propose some re-engineering for this issue.
(I mean something cleanner than just initialising to 0 those variables).

Cheers,
Sylvain