Address NullReferenceException in Anti-Malware Realtime Scans View

[brianrob]

• Address NullReferenceException when there is a missing process event.
• Show all scans even when the filter driver events aren't present. This is especially useful when looking at traces generated by New-MpPerformanceRecording. These events will show up with an "Unknown" reason and won't have a stack, since these are both generated by the filter driver events.