Fixes an error in the "An unfiltered thread should have at least 1 instruction" drmemtrace invariant where it does not consider a no-fetch or prefetch instruction.
(If I've sent you too many reviews please load balance by assigning someone else...but they all overlap and all but PR #6598 are small so it seemed easiest for one person to see all of them.)
Fixes an error in the "An unfiltered thread should have at least 1 instruction" drmemtrace invariant where it does not consider a no-fetch or prefetch instruction.
Adds a unit test which fails without the fix.
Fixes #6622