Remove double negation

Author: vmcj

docker-contributor/scripts/start.sh

@@ -2,7 +2,7 @@
 
 function file_or_env {
     file=${1}_FILE
-    if [ ! -z "${!file}" ]; then
+    if [ -n "${!file}" ]; then
         cat "${!file}"
     else
         echo -n "${!1}"

docker-gitlabci/build.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -e
 
-if [[ ! -z ${CI} ]]
+if [[ -n ${CI} ]]
 then
         set -euxo pipefail
         export PS4='(${0}:${LINENO}): - [$?] $ '

docker/domserver/scripts/start.d/50-domjudge.sh

@@ -2,7 +2,7 @@
 
 function file_or_env {
     file=${1}_FILE
-    if [ ! -z "${!file}" ]; then
+    if [ -n "${!file}" ]; then
         cat "${!file}"
     else
         echo -n "${!1}"

docker/judgehost/scripts/start.sh

@@ -2,7 +2,7 @@
 
 function file_or_env {
     file=${1}_FILE
-    if [ ! -z "${!file}" ]; then
+    if [ -n "${!file}" ]; then
         cat "${!file}"
     else
         echo -n "${!1}"