PHP warning message during 1.8/1.9/1.10/15.04 -> 15.10 upgrade of a completely new site

[Aaron Wells]

To replicate:

1. Clean install of 15.04.3
2. Upgrade to 15.10_STABLE

Result:

The upgrade proceeds okay, but you see this warning message:

[DBG] c7 (lib/db/upgrade.php:4164) Add user_login_data table to record when a user logs in
[WAR] c7 (lib/db/upgrade.php:4178) Invalid argument supplied for foreach()
Call stack (most recent first):

    log_message("Invalid argument supplied for foreach()", 8, true, true, "/home/aaronw/www/mahara-clients/htdocs/lib/db/upgr...", 4178) at /home/aaronw/www/mahara-clients/htdocs/lib/errors.php:441
    error(2, "Invalid argument supplied for foreach()", "/home/aaronw/www/mahara-clients/htdocs/lib/db/upgr...", 4178, array(size 18)) at /home/aaronw/www/mahara-clients/htdocs/lib/db/upgrade.php:4178
    xmldb_core_upgrade("2015030417") at /home/aaronw/www/mahara-clients/htdocs/lib/upgrade.php:359
    upgrade_core(object(stdClass)) at /home/aaronw/www/mahara-clients/htdocs/admin/upgrade.json.php:90

[Aaron Wells (u-aaronw)]

This problem only occurs if there is no record in the database that matches "select * from usr where deleted=0 and lastlogin is not null".

In other words, if it's a site that absolutely no one has ever logged into. So, it's only something you'll encounter if, like me, you're a dev who does a clean install from the command-line, and then upgrades.