Now that we no longer always call context_acquire() from
swapchain_init(), context acquisition can fail here instead.
This fixes a regression introduced by commit
64d41b3d.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=47468Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>