Skip VulkanBarriersPerfBenchmark on NV/Win. This test is failing because our out-of-date Windows 7 NV bots can't create a GLES 3.0 context. Skip this test until the machines are updated. Also updates our wrapper classes to check for an empty handle before calling delete. Prevents a crash trying to call null functions. Bug: chromium:1090139 Change-Id: I0bb58f8bd167691cd241fb0df30cdf4b2f6adf5b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2225447 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>