dri3: Fix MakeCurrent without a default framebuffer

In OpenGL 3.0 and later it is legal to make a context current without
a default framebuffer.

This has been broken since DRI3 support was introduced.

Cc: "13.0 12.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
1 file changed