import-sql failes if PSQL_OPTIONS is not set or empty

[JensTimmerman]

When running import-sql I get the error

Importing openmaptiles.sql (md5 fc418c3ac5dfa1ae4328cc6d121fbb51  -  4416 lines) into Postgres...
./import-sql: line 28: psql_opts[@]: unbound variable

export PSQL_OPTIONS= doesn't make a difference I have to set export PSQL_OPTIONS=-a before the script works.