Handler corner case where GID already exists

Author: Chuxel

script-library/docker-debian.sh

@@ -283,7 +283,7 @@ log "Ensuring ${USERNAME} has access to ${SOURCE_SOCKET} via ${TARGET_SOCKET}"
 # that we can set permissions on it without affecting the host.
 if [ "${ENABLE_NONROOT_DOCKER}" = "true" ] && [ "${SOURCE_SOCKET}" != "${TARGET_SOCKET}" ] && [ "${USERNAME}" != "root" ] && [ "${USERNAME}" != "0" ]; then
     SOCKET_GID=\$(stat -c '%g' ${SOURCE_SOCKET})
-    if [ "\${SOCKET_GID}" != "0" ] && [ "\${SOCKET_GID}" != "${DOCKER_GID}" ]; then
+    if [ "\${SOCKET_GID}" != "0" ] && [ "\${SOCKET_GID}" != "${DOCKER_GID}" ] && ! grep -E ".+:x:\${SOCKET_GID}" /etc/group; then
         sudoIf groupmod --gid "\${SOCKET_GID}" docker
     else
         # Enable proxy if not already running