Safeguard against colour output in grep commandadd -i to grep to make search for "Location" case-insensitive

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

automated install/basic-install.sh

@@ -2382,17 +2382,14 @@ FTLcheckUpdate() {
         if [[ ${ftlLoc} ]]; then
             local FTLversion
             FTLversion=$(/usr/bin/pihole-FTL tag)
-            local FTLreleaseData
             local FTLlatesttag
 
-            if ! FTLreleaseData=$(curl -sI https://github.com/pi-hole/FTL/releases/latest); then
+            if ! FTLlatesttag=$(curl -sI https://github.com/pi-hole/FTL/releases/latest | grep --color=never -i Location | awk -F / '{print $NF}' | tr -d '[:cntrl:]'); then
                 # There was an issue while retrieving the latest version
                 printf "  %b Failed to retrieve latest FTL release metadata" "${CROSS}"
                 return 3
             fi
 
-            FTLlatesttag=$(grep 'Location' <<< "${FTLreleaseData}" | awk -F '/' '{print $NF}' | tr -d '\r\n')
-
             if [[ "${FTLversion}" != "${FTLlatesttag}" ]]; then
                 return 0
             else