The EGL spec does not specifically call out how to handle the case
where 'value' passed to eglGetSyncAttribKHR is NULL, however many
implementations will set the context error to EGL_BAD_PARAMETER
and return without crashing. dEQP has a test which specifically
checks for this behavior. Align SwiftShader's implementation with
other EGL implementations.

Bug: b/74572503
Test: dEQP-EQL GetSyncInvalidValueTest
Change-Id: Ic893cd7073c12c463ded78042031df1bf85f6ce2
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28028Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alistair Strachan <astrachan@google.com>