GH_TOKEN is always empty string as initialized

github/github-membership.sh

@@ -48,7 +48,6 @@ Options:
 }
 
 ACTION=""
-GH_TOKEN=""
 
 while getopts "apj" opt; do
     case "${opt}" in
@@ -75,7 +74,7 @@ fi
 
 shift $((OPTIND-1))
 
-if [ -z "$GH_TOKEN" ]; then
+if [[ -z "${GH_TOKEN:-}" ]]; then
   read -p "Enter your GitHub token: " -r GH_TOKEN
   export GH_TOKEN
 fi