Fix shellcheck complains

scripts/enforce_labels.bash

@@ -15,14 +15,14 @@ if ! docker inspect --type=image "$1" > /dev/null ; then
 fi
 
 for label in "${!enforced_labels[@]}" ; do
-    if ! docker inspect -f "{{json .Config.Labels }}" "$image_name" | jq -e '.['\"$label\"']' > /dev/null ; then 
+    if ! docker inspect -f "{{json .Config.Labels }}" "$image_name" | jq -e '.['\""$label"\"']' > /dev/null ; then
         echo "Key not found"
         echo "$label = ${enforced_labels[$label]}"
         label_args+=" --label $label=\"${enforced_labels[$label]}\""
     fi
 done
 
-if [ -v label_args ]; then 
+if [ -n "${label_args+x}" ]; then
     run_command="echo \"FROM $image_name\" | docker build $label_args -t $image_name -"
     eval "$run_command"
 fi