sequencer - addconf: allow empty source and fix printf missing newline

sequencer.sh

@@ -866,7 +866,7 @@ addConf() {
     esac
   done
 
-  local source="${1:?}"
+  local source="${1:-}"
   local dest="${2:?}"
 
   if [ "${transferCmd}" == "cat" ] && [ ! -f "${source}" ] ; then
@@ -905,7 +905,7 @@ addConf() {
         else
           "${transferCmd}" "${source}" >> "${dest}"
         fi
-        sqr::printf 'ok\n [i] %s' "Existing config saved to ${addConfBackup}"
+        sqr::printf 'ok\n [i] %s\n' "Existing config saved to ${addConfBackup}"
         return 0
       else
         sqr::echo "nok"