Add some code that should avoid crashes seen in the wild

Author: jasonleenaylor

src/SIL.LCModel/DomainImpl/Vectors.cs

@@ -1329,12 +1329,15 @@ public virtual T this[int index]
 		/// </remarks>
 		public int IndexOf(T obj)
 		{
-			lock (SyncRoot)
+			if (obj != null)
 			{
-				// No need to fluff items up!
-				for (int i = 0; i < m_items.Count; i++)
-					if (m_items[i].Id == obj.Id)
-						return i;
+				lock (SyncRoot)
+				{
+					// No need to fluff items up!
+					for (int i = 0; i < m_items.Count; i++)
+						if (m_items[i].Id == obj.Id)
+							return i;
+				}
 			}
 			return -1;
 		}

src/SIL.LCModel/DomainServices/AnalysisOccurrence.cs

@@ -56,7 +56,7 @@ public virtual IAnalysis Analysis
 		{
 			get
 			{
-				if(Index < Segment.AnalysesRS.Count)
+				if (Segment?.AnalysesRS != null && Index < Segment.AnalysesRS.Count)
 					return Segment.AnalysesRS[Index];
 				return null;
 			}

src/SIL.LCModel/Infrastructure/Impl/RepositoryAdditions.cs

@@ -366,10 +366,7 @@ internal partial class ConstituentChartCellPartRepository
 		/// </summary>
 		public IEnumerable<IConstituentChartCellPart> InstancesWithChartCellColumn(ICmPossibility target)
 		{
-			((ICmObjectRepositoryInternal)m_cache.ServiceLocator.ObjectRepository).EnsureCompleteIncomingRefsFrom(
-				ConstituentChartCellPartTags.kflidColumn);
-			return ((ICmObjectInternal)target).IncomingRefsFrom(ConstituentChartCellPartTags.kflidColumn).Cast
-					<IConstituentChartCellPart>();
+			return AllInstances().Where(cccp => cccp.ColumnRA == target);
 		}
 	}
 	#endregion