VS: Avoid crash with VS 2015 when all SDKs are higher than 10.0.14393.0
Move the filter added by !2388 (merged) to before our check that the remaining list is empty. Otherwise we crash when dereferencing the first entry of an empty vector.
Also add a comment explaining where 10.0.14393.0 came from.
Fixes: #18633 (closed)
Topic-rename: vs2015-no-sdk
Edited by Brad King