Audit CollectOSS for issues with blank config

While testing #311 (specifically the new startup sequence, alongside other things), i introduced a bug that corrupted a couple settings in the config table. The impact was only my test instance, however i discovered that deleting these values, one of which was `logs_directory`, caused CollectOSS to not start up because the built in logger was checking for the value in a way that would crash if the value was missing.

This needs cleaning up, both in this specific case, and also in general, because it may cause issues when we fix #132 otherwise