Do not overwrite existing webmail alias during upgrade

install/upgrade/0.10.0-190430.sh

@@ -6,7 +6,7 @@ HESTIA_BACKUP="/root/hst_upgrade/$(date +%d%m%Y%H%M)"
 hestiacp="$HESTIA/install/deb"
 
 # Add webmail alias variable to system configuration if non-existent
-webmail_alias_check=$(cat $HESTIA/conf/hestia.conf | grep WEBMAIL_ALIAS)
+WEBMAIL_ALIAS_CHECK=$(cat $HESTIA/conf/hestia.conf | grep WEBMAIL_ALIAS)
 if [ -z "$WEBMAIL_ALIAS_CHECK" ]; then
     echo "(*) Adding global webmail alias to system configuration..."
     sed -i "/WEBMAIL_ALIAS/d" $HESTIA/conf/hestia.conf