[BUG] incorrect shell syntax in postgres/Dockerfile

[dmd]

1. Clone repository.
2. do docker-compose up

Status: Downloaded newer image for postgres:12.2-alpine
 ---> ae192c4d3ada
Step 2/3 : RUN if [ ! -z ${POSTGRES_GID} && ${POSTGRES_GID} != 70 ]; then         sed -i'' -E 's/postgres:x:70:postgres/postgres:x:'${POSTGRES_GID}':postgres/' /etc/group;         sed -i'' -E 's/postgres:x:70:70:/postgres:x:'${POSTGRES_UID}':'${POSTGRES_GID}':/' /etc/passwd;     fi;
 ---> Running in ca4bb2bd2bef
sh: missing ]