Modify emit_dict to include symbols when b is empty

[kivattik]

If only removals occurred, 'smatched' is never incremented defaulting s==1. To print the entire list of changes, also check for whether any changes occurred before returning an empty dict.

[fzumstein]

Could you please add a test?

[kivattik]

Of course.

[fzumstein]

replaced by #64