Fix start if dir already exists.

Dockerfile

@@ -1,5 +1,4 @@
 FROM alpine:latest
-LABEL homepage=https://git.redxef.duckdns.org/
 
 RUN apk update && apk upgrade && apk add nginx gettext && \
     rm -r /etc/nginx

start-nginx.sh

@@ -25,7 +25,7 @@ sub_env_vars="$(cat /environment_variables.txt)"
 echo "Enabling servers"
 (
     cd "/etc/nginx/sites-available" || exit $?
-    mkdir "../sites-enabled" || exit $?
+    test -d "../sites-enabled" || mkdir "../sites-enabled"
     for f in *.conf; do
         envsubst "$sub_env_vars" < "$f" > "../sites-enabled/$f"
     done