dont crash when organizing firmware

BizHawk.Client.Common/FirmwareManager.cs

@@ -46,6 +46,7 @@ namespace BizHawk.Client.Common
 			_resolutionDictionary.TryGetValue(record, out resolved);
 
 			// couldnt find it! do a scan and resolve to try harder
+			// NOTE: this could result in bad performance in some cases if the scanning happens repeatedly..
 			if (resolved == null && first)
 			{
 				DoScanAndResolve();

BizHawk.Client.EmuHawk/config/FirmwaresConfig.cs

@@ -264,6 +264,7 @@ namespace BizHawk.Client.EmuHawk
 			foreach (var fr in FirmwareDatabase.FirmwareRecords)
 			{
 				var ri = Manager.Resolve(fr);
+				if (ri == null) continue;
 				if (ri.KnownFirmwareFile == null) continue;
 				if (ri.UserSpecified) continue;