functions: fix linking support for official postgres image

assets/runtime/functions

@@ -169,6 +169,7 @@ nextcloud_finalize_database_parameters() {
     # support for linked official postgres image
     DB_USER=${DB_USER:-$POSTGRESQL_ENV_POSTGRES_USER}
     DB_PASS=${DB_PASS:-$POSTGRESQL_ENV_POSTGRES_PASSWORD}
+    DB_NAME=${DB_NAME:-$POSTGRESQL_ENV_POSTGRES_DB}
     DB_NAME=${DB_NAME:-$DB_USER}
 
     # support for linked sameersbn/postgresql image