Fix a few unit tests

Core/Calculation/EventAssigner.cs

@@ -29,6 +29,7 @@ namespace Core.Calculation
 			_eventPickCounts = new int[_allEvents.Length];
 			_preAssigned = new List<EventAssignment>();
 			_droppedEvents = new List<CompetitiveEvent>();
+            _includedEvents = new List<CompetitiveEvent>();
 			for (var i = 0; i < _events.Count; i++)
 			{
 				var e = _events[i];

Core/Parsers/AssignmentAssumptionParser.cs

@@ -17,7 +17,9 @@ public class AssignmentAssumptionParser : CsvParserBase
 		var studentColumns =
 			CsvReader.HeaderRecord.Select(h => h.Trim()).Where(h => !string.IsNullOrEmpty(h)).ToArray();
 
-		var studentArray = studentColumns.Select(c => students.First(s => s.FirstName == c)).ToArray();
+		var studentArray = 
+            studentColumns
+                .Select(c => students.FirstOrDefault(s => s.FirstName == c)).ToArray();
 
 		while (CsvReader.Read())
 		{