Automation Hub backup fails when automationhub_pg_port=''

Issue

When Automation Hub is installed with an inventory file containing automationhub_pg_port='', subsequent backup (./setup.sh -b) attempts will fail with an error like the following:

TASK [ansible.automation_platform_installer.backup : Perform a PostgreSQL dump.] ***
fatal: [a.b.c.d]: FAILED! => {"changed": false, "msg": "argument 'port' is of type <class 'str'> and we were unable to convert to int: <class 'str'> cannot be converted to an int"}