Fix memory leak when default framebuffer has 0 depth bits and 0 stencil bits

Change-Id: If9dbcfc7eac3295b2523dd41dc87198d1b1e2d76
Reviewed-on: https://chromium-review.googlesource.com/229022
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Austin Kinross <aukinros@microsoft.com>