Poller functions may not run if 'processes' table is missing

[netniV]

Describe the bug

If, for some reason, the processes table is missing, certain poller functions such as maintenance will not run and silently exists.

To Reproduce

Steps to reproduce the behavior:

1. Remove the 'processes' table

2. Run poller_maintence.php

3. See no error but also no maintenance

Expected behavior

If the processes table is required, this should be recorded as an error. If it is not required, when the table is missing the register_process_start() function should return true instead of false.