Replace == on -z

data_from_portwine/scripts/functions_helper

@@ -267,7 +267,7 @@ EOF
                     while [[ ! $line =~ msgid ]] ; do
                         msgstr+=$line
                         read -r line
-                        if [[ $line == "" ]] ; then
+                        if [[ -z $line ]] ; then
                             break
                         fi
                     done
@@ -756,8 +756,8 @@ background_pid () {
                 export bg_pid"${arg3}"="$PID" ;;
             --end)
                 PID=$(get_bg_pid bg_pid"${arg3}")
-                [[ $PID == "" ]] && return 1
-                wait "$PID" && return 0 ;;
+                [[ -z $PID ]] && return 1
+                wait "$PID" 2>/dev/null && return 0 ;;
         esac
     fi
 }
@@ -1016,10 +1016,10 @@ seconds_to_time () {
     if [[ $minutes =~ ^0$ ]] ; then
         hours=${hours//" ${translations[and]} "/}
         minutes=
-        if [[ $days == "" ]] || [[ $hours == "" ]] ; then
+        if [[ -z $days ]] || [[ -z $hours ]] ; then
             days=${days//","/}
         fi
-        if [[ $days == "" ]] && [[ $hours == "" ]] ; then
+        if [[ -z $days ]] && [[ -z $hours ]] ; then
             minutes="${translations[less than a minute]}"
         fi
     elif [[ $minutes =~ ^1$ ]] ; then