Fix warnings in multiple classes

[DimonByte]

Severity Code Description Project File Line Suppression State
Warning (active) CS8604 Possible null reference argument for parameter 'path' in 'DirectoryInfo Directory.CreateDirectory(string path)'. SinkDNS \SinkDNS\Modules\SinkDNSInternals\TaskScheduler.cs 160
Warning (active) CS8601 Possible null reference assignment. SinkDNS \SinkDNS\Modules\DNSCrypt\DNSCryptQueryMonitor.cs 124
Warning (active) CS8603 Possible null reference return. SinkDNS \SinkDNS\Modules\DNSCrypt\ServiceManager.cs 74
Warning (active) CS8603 Possible null reference return. SinkDNS \SinkDNS\Modules\DNSCrypt\ServiceManager.cs 118
Warning (active) CS8603 Possible null reference return. SinkDNS \SinkDNS\Modules\DNSCrypt\ServiceManager.cs 123
Warning (active) CS8618 Non-nullable field 'fileWatcher' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable. SinkDNS \SinkDNS\Modules\DNSCrypt\DNSCryptQueryMonitor.cs 40
Warning (active) CS8618 Non-nullable field '_cancellationTokenSource' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable. SinkDNS \SinkDNS\Modules\DNSCrypt\DNSCryptQueryMonitor.cs 40
Warning (active) CS8618 Non-nullable field '_pollingTask' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable. SinkDNS \SinkDNS\Modules\DNSCrypt\DNSCryptQueryMonitor.cs 40
Warning (active) CS8618 Non-nullable event 'OnDomainBlocked' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the event as nullable. SinkDNS \SinkDNS\Modules\DNSCrypt\DNSCryptQueryMonitor.cs 40