best way to handle null vs list/dict returns?

[Eric Arnold]

This seems like a klunky way of getting a value from getbufvar().

                        let attach_to = {}
                        if len( getbufvar( bufnr, 'attach_to' ) ) > 0
                                let attach_to = getbufvar( bufnr, 'attach_to' )
                        endif
                        if len( attach_to ) > 0

If I simply use

                        let attach_to = {}
                        let attach_to = getbufvar( bufnr, 'attach_to' )
                        if len( attach_to ) > 0
                                 .......
it will fail on variable type when the target for getbufvar(), i.e.
b:attach_to  doesn't exist.  Fortunately,  len()  is smart enough to
take different types, so there is a workaround.

I don't know if there's a good way around this without easing up on
the variable type-checking, and [re-]initialize variables to the
correct type upon assignment.  This would make life soooooo much
easier with Vim 7 script.