Use $object->sqlValue('NULL') (identical to DataObject_Cast'ing) instead and
fix related issues like (email|sms)settings considering these NULLs as a
false positive for the E-Mail address still being set when it's been removed.
There could also be security implications to the now-disabled approach of
considering 'NULL' strings as SQL NULLs.
The code used to operate under the assumption that MariaDB doesn't support
quoting identifiers. Not only is that not exactly true, but MariaDB has
reserved keywords that cannot be used as table or column names unquoted.
Issue description as reported by aab:
2019-08-28 17:34:48 LOG_ERR: [khp.ignorelist.com:61055.f5f7f51c GET /api/statuses/show/178372.atom] ServerErrorAction: 500 Class 'OAuthRequest' not found
2019-08-28 17:39:50 LOG_ERR: [khp.ignorelist.com:65390.4483ff85 GET /api/statusnet/conversation/104672.rss] Handled serverError (500) but cannot output into desired format ('rss'): 'Class \'OAuthRequest\' not found'
2019-08-28 17:39:50 LOG_ERR: [khp.ignorelist.com:65390.4483ff85 GET /api/statusnet/conversation/104672.rss] ServerErrorAction: 500 Class 'OAuthRequest' not found
2019-08-28 17:40:49 LOG_ERR: [khp.ignorelist.com:65390.4c745f68 GET /api/statuses/show/18132.atom] Handled serverError (500) but cannot output into desired format ('atom'): 'Class \'OAuthRequest\' not found'
2019-08-28 17:40:49 LOG_ERR: [khp.ignorelist.com:65390.4c745f68 GET /api/statuses/show/18132.atom] ServerErrorAction: 500 Class 'OAuthRequest' not found
2019-08-28 17:47:41 LOG_ERR: [khp.ignorelist.com:65390.42ee9fd4 GET /api/statusnet/conversation/133023.as] Handled serverError (500) but cannot output into desired format ('as'): 'Class \'OAuthRequest\' not found'
