Fix check_env function

gitlab/functions.sh

@@ -27,7 +27,7 @@ log_error() {
 
 # Checks a given environment variable is set (non-zero size)
 check_env() {
-  if [ -z "${!${1}}" ]; then
+  if [ -z "${!1}" ]; then
     log_error "Variable ${1} is undefined - aborting...";
     exit 1
   else