Add support for Automation under PHP 8

[TheWitness]

Describe the bug

When automation runs, Cacti throws a few DEPRECATION errors upon startup.

2022-02-15  00:32:34 - CMDPHP PHP ERROR Backtrace:   (/poller_automation.php[285]:automation_primeIPAddressTable(),  /lib/api_automation.php[3338]:automation_calculate_start(),  /lib/api_automation.php[3272]:automation_get_network_info(),  /lib/api_automation.php[3234]:automation_get_network_info(),  /lib/api_automation.php[3247]:CactiErrorHandler())
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2022-02-15 00:32:34 - ERROR PHP DEPRECATED: Automatic conversion of  false to array is deprecated in file:  /var/www/html/cacti/lib/api_automation.php  on line: 3247
2022-02-15 00:32:34 - CMDPHP PHP ERROR Backtrace:   (/poller_automation.php[285]:automation_primeIPAddressTable(),  /lib/api_automation.php[3335]:automation_calculate_total_ips(),  /lib/api_automation.php[3284]:automation_get_network_info(),  /lib/api_automation.php[3234]:automation_get_network_info(),  /lib/api_automation.php[3247]:CactiErrorHandler())
2022-02-15 00:32:34 - ERROR PHP DEPRECATED: Automatic conversion of  false to array is deprecated in file:  /var/www/html/cacti/lib/api_automation.php  on line: 3247

Expected behavior

Cacti should be free of these backtraces.