VertexArray::syncState syncs all dirty bits, including
DIRTY_BIT_ELEMENT_ARRAY_BUFFER even for draw calls that don't use this
buffer, such as glDrawArrays.  If the element buffer is given 0 size,
this caused a crash in the Vulkan backend.

Bug: chromium:1172577
Change-Id: I02d78c9660c07b896f7403867b648901478251fe
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2701831Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>