To rephrase that,
You would like alias("") to be silently ignored instead of generating an error.
That is a change of semantics, but I can see your point and the change would be backward compatible. Could also be added as a behavior that needs activation from the st.cmd.
Are you aware of the other way to specify aliases, loading them in a separate file?
This can't be used inside of templates, but it keeps concerns better separated: Always load the template, then load alias definitions if you need them.
Cheers,
~Ralph