In ieee.bbx, \addspace is used to separate the bibstring number and the field number. The same is true for the volume and maybe other fields as well.
This can lead to unwanted line breaks between the bibstring and the field. I manually replaced \addspace by \addnbspace, maybe this could be the default behaviour or a package option.
Probably the formatting should be applied at the \DeclareFieldFormat stage in any case, with the bibmacro just putting in the correct fields with no hard-coded formatting. I'll adjust.
In ieee.bbx,
\addspace
is used to separate the bibstringnumber
and the fieldnumber
. The same is true for the volume and maybe other fields as well.This can lead to unwanted line breaks between the bibstring and the field. I manually replaced
\addspace
by\addnbspace
, maybe this could be the default behaviour or a package option.