Leave the cursor alone when no tag was opened

Refusing the address of a single selected tag leaves the quickfix list empty,
and 'normal! ^zvzz' then moved the cursor in whatever buffer the user was in.

autoload/fzf/vim.vim

@@ -547,6 +547,7 @@ function! s:sandboxed(cmd)
   return 'sandbox execute '.string(a:cmd)
 endfunction
 
+
 " Address of a tag, given the rest of the line after the file name, or, with
 " 'whole' off, the address field alone as :BTags reads it. Only the forms a tags
 " file is meant to hold, a line number and a search pattern, chained with ';' for
@@ -1735,7 +1736,7 @@ function! s:btags_sink(from, lines)
     normal! g`'
     " Because 'listproc' will use 'cfirst' to go to the first item in the list
     call s:fill_quickfix('btags', qfl)
-  else
+  elseif len(qfl) == 1
     normal! zvzz
   endif
   if !empty(tagname)
@@ -1835,7 +1836,7 @@ function! s:tags_sink(from, lines)
     call s:action_for(key, qfl[0].filename, 1)
 
     call s:fill_quickfix('tags', qfl)
-  else
+  elseif len(qfl) == 1
     normal! ^zvzz
   endif
   if !empty(tagname)