fix: correct the validation message

common-functions

@@ -735,7 +735,7 @@ verify_service_name() {
 is_valid_service_name() {
   declare desc="Validates a service name"
   declare SERVICE="$1"
-  [[ -z "$SERVICE" ]] && dokku_log_fail "SERVICE must not be null"
+  [[ -z "$SERVICE" ]] && return 1
 
   if [[ "$SERVICE" =~ ^[A-Za-z0-9_]+$ ]]; then
     return 0