Fix unbound variable errors

seqs/friendica.sh

@@ -35,10 +35,10 @@ step_20() {
     error -e "No configuration file found"
     return 1
   fi
-  if [ ! -z $FR_BACKUP ] ; then
+  if [ -n "$FR_BACKUP" ] ; then
     exe mkdir -p "$FR_BACKUP"
   fi
-  if [ ! -z "$1" ] ; then
+  if [ -n "${1:-}" ] ; then
     tempRoot="$1"
   else
     tempRoot="$FR_LOC"
@@ -61,7 +61,7 @@ step_20() {
 
 step_22_info() {
   shift
-  if [ -z $1 ] ; then
+  if [ -z "${1:-}" ] ; then
     echo -n "Get latest version from github"
     if ! contextHelp ; then
       echo ": $(curl --silent "$latestUrl" | grep -Po '"tag_name": "\K.*?(?=")')"
@@ -76,7 +76,7 @@ step_22_alias() { echo "upgrade"; }
 step_22() {
   shift # don't need step number
   local latestVersion=
-  if [ ! -z $1 ] ; then
+  if [ -n "${1:-}" ] ; then
     latestVersion="$1"
   else
     latestVersion=$(curl --silent "$latestUrl" | grep -Po '"tag_name": "\K.*?(?=")')