[SampleProfile] Fix bug where remapper returns empty string and crashing...

[SampleProfile] Fix bug where remapper returns empty string and crashing Sample Profile loader (#71479)

Normally SampleContext does not allow using an empty StirngRef to
construct an object, this is to prevent bugs reading the profile.
However empty names may be emitted by a function which its name is
intentionally set to empty, or a bug in the remapper that returns an
empty string. Regardless, converting it to FunctionId first will prevent
the assert, and that assert check is unnecessary, which will be
addressed in another patch