Restore the package name to overload errors; fix crash

Restore the package name to overload errors; fix crash

Commit bfcb351493b (which was backported to 5.8.8) caused these error
messages always to mention the overload package, instead of the pack-
age involved:

Can't resolve method "foo" overloading "+" in package "baz"
Stub found while resolving method "foo" overloading "+" in package "baz"

This commit fixes that.  A compiler warning alerted me to the possi-
bility of HvNAME being null, so I wrote a small test for that, found
that it crashed, and incorporated the fix for the crash into the same
commit (since it’s the same line of code).