fix check whether setting is present

home.admin/_background.sh

@@ -69,7 +69,7 @@ do
     echo "*** RECHECK UNDERVOLTAGE ***"
     countReports=$(sudo cat /var/log/syslog | grep -c "Under-voltage detected!")
     echo "${countReports} undervoltage reports found in syslog"
-    if [ ${#undervoltageReports} -eq 0 ]; then
+    if ! grep -Eq "^undervoltageReports=" ${infoFile}; then
       # write new value to info file
       undervoltageReports="${countReports}"
       echo "undervoltageReports=${undervoltageReports}" >> ${infoFile}