[Beta 9.1][Commerce] Exception when adding a product custom field

Clicking on the + Create New button for a new product's Custom Field throws this exception:

Whoops\Exception\ErrorException thrown with message "explode(): Passing null to parameter #2 ($string) of type string is deprecated"

Stacktrace:
#8 Whoops\Exception\ErrorException in \applications\nexus\sources\Package\CustomField.php:153
#7 explode in \applications\nexus\sources\Package\CustomField.php:153
#6 IPS\nexus\Package\CustomField:form in \system\Node\Controller.php:567
#5 IPS\Node\Controller:_addEditForm in \system\Node\Controller.php:464
#4 IPS\Node\Controller:form in \system\Dispatcher\Controller.php:128
#3 IPS\Dispatcher\Controller:execute in \system\Node\Controller.php:117
#2 IPS\Node\Controller:execute in \applications\nexus\modules\admin\store\fields.php:56
#1 IPS\nexus\modules\admin\store\fields:execute in \system\Dispatcher\Dispatcher.php:169
#0 IPS\Dispatcher:run in \admin\index.php:15

Based on Whoops debug code, the issue is that the $this->packages variable on line 153 is NULL:

        foreach ( array_filter( explode( ',', $this->packages ) ) as $id )
        {
            try
            {
                $packages[] = Package::load( $id );
            }
            catch ( OutOfRangeException ) { }
        }

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P.S.: Merry Christmas! 🎅🎄🤶

I'll be posting a few more bugs as your gift! 😋