Fix an iterator invalidation bug in SSAupdater
Fix an iterator invalidation bug in SSAupdater

I failed to create a test, but will check in a test in the context of
redundant load elimination, which will use the SSAupdater.

khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift,khizkhiz/swift