Merge pull request #2820 from pi-hole/fix/ftl-update-no-network

Fix pihole -up showing FTL update when network is down

automated install/basic-install.sh

@@ -2396,8 +2396,16 @@ FTLcheckUpdate() {
         if [[ ${ftlLoc} ]]; then
             local FTLversion
             FTLversion=$(/usr/bin/pihole-FTL tag)
+            local FTLreleaseData
             local FTLlatesttag
-            FTLlatesttag=$(curl -sI https://github.com/pi-hole/FTL/releases/latest | grep 'Location' | awk -F '/' '{print $NF}' | tr -d '\r\n')
+
+            if ! FTLreleaseData=$(curl -sI https://github.com/pi-hole/FTL/releases/latest); 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