diff --git a/src/AddIns/Misc/UsageDataCollector/UsageDataSessionWriter.cs b/src/AddIns/Misc/UsageDataCollector/UsageDataSessionWriter.cs
index 6844e59829..0c432a29cf 100644
--- a/src/AddIns/Misc/UsageDataCollector/UsageDataSessionWriter.cs
+++ b/src/AddIns/Misc/UsageDataCollector/UsageDataSessionWriter.cs
@@ -159,6 +159,8 @@ namespace ICSharpCode.UsageDataCollector
 		/// <returns>ID that can be used for <see cref="WriteEndTimeForFeature"/></returns>
 		public long AddFeatureUse(string featureName, string activationMethod)
 		{
+			if (featureName == null)
+				throw new ArgumentNullException("featureName");
 			long featureRowId;
 			using (SQLiteTransaction transaction = this.connection.BeginTransaction()) {
 				using (SQLiteCommand cmd = this.connection.CreateCommand()) {
@@ -196,6 +198,8 @@ namespace ICSharpCode.UsageDataCollector
 		/// <param name="stacktrace">Stacktrace</param>
 		public void AddException(string exceptionType, string stacktrace)
 		{
+			if (exceptionType == null)
+				throw new ArgumentNullException("exceptionType");
 			using (SQLiteCommand cmd = this.connection.CreateCommand()) {
 				cmd.CommandText = "INSERT INTO Exceptions (session, time, type, stackTrace)" +
 					" VALUES (?, datetime('now'), ?, ?);";
diff --git a/src/AddIns/Misc/UsageDataCollector/UsageDataUploader.cs b/src/AddIns/Misc/UsageDataCollector/UsageDataUploader.cs
index 887107bec5..d06886fa14 100644
--- a/src/AddIns/Misc/UsageDataCollector/UsageDataUploader.cs
+++ b/src/AddIns/Misc/UsageDataCollector/UsageDataUploader.cs
@@ -185,7 +185,8 @@ namespace ICSharpCode.UsageDataCollector
 						if (!reader.IsDBNull(2))
 							featureUse.EndTime = reader.GetDateTime(2);
 						featureUse.FeatureName = stringInterning.Intern(reader.GetString(3));
-						featureUse.ActivationMethod = stringInterning.Intern(reader.GetString(4));
+						if (!reader.IsDBNull(4))
+							featureUse.ActivationMethod = stringInterning.Intern(reader.GetString(4));
 						session.FeatureUses.Add(featureUse);
 					}
 				}
@@ -201,7 +202,8 @@ namespace ICSharpCode.UsageDataCollector
 						UsageDataException exception = new UsageDataException();
 						exception.Time = reader.GetDateTime(1);
 						exception.ExceptionType = stringInterning.Intern(reader.GetString(2));
-						exception.StackTrace = stringInterning.Intern(reader.GetString(3));
+						if (!reader.IsDBNull(3))
+							exception.StackTrace = stringInterning.Intern(reader.GetString(3));
 						session.Exceptions.Add(exception);
 					}
 				}
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs
index 23b1149973..36ef8ece7c 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs
@@ -22,7 +22,7 @@ namespace ICSharpCode.AvalonEdit.Folding
 	/// <summary>
 	/// Stores a list of foldings for a specific TextView and TextDocument.
 	/// </summary>
-	public class FoldingManager
+	public class FoldingManager : IWeakEventListener
 	{
 		internal readonly TextView textView;
 		internal readonly TextDocument document;
@@ -41,7 +41,39 @@ namespace ICSharpCode.AvalonEdit.Folding
 				throw new ArgumentNullException("document");
 			this.textView = textView;
 			this.document = document;
-			this.foldings = new TextSegmentCollection<FoldingSection>(document);
+			this.foldings = new TextSegmentCollection<FoldingSection>();
+			document.VerifyAccess();
+			TextDocumentWeakEventManager.Changed.AddListener(document, this);
+		}
+		#endregion
+		
+		#region ReceiveWeakEvent
+		/// <inheritdoc/>
+		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			if (managerType == typeof(TextDocumentWeakEventManager.Changed)) {
+				OnDocumentChanged((DocumentChangeEventArgs)e);
+				return true;
+			}
+			return false;
+		}
+		
+		bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			return ReceiveWeakEvent(managerType, sender, e);
+		}
+		
+		void OnDocumentChanged(DocumentChangeEventArgs e)
+		{
+			foldings.UpdateOffsets(e);
+			FoldingSection s = foldings.FindFirstSegmentWithStartAfter(e.Offset);
+			while (s != null && s.StartOffset == e.Offset) {
+				FoldingSection next = foldings.GetNextSegment(s);
+				if (s.Length == 0) {
+					RemoveFolding(s);
+				}
+				s = next;
+			}
 		}
 		#endregion
 		
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingSection.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingSection.cs
index 8ca722ddc1..43c3aabd7e 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingSection.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingSection.cs
@@ -40,10 +40,7 @@ namespace ICSharpCode.AvalonEdit.Folding
 							}
 						}
 					} else {
-						if (collapsedSection != null) {
-							collapsedSection.Uncollapse();
-							collapsedSection = null;
-						}
+						RemoveCollapsedLineSection();
 					}
 					if (manager != null)
 						manager.textView.Redraw(this, DispatcherPriority.Normal);
@@ -74,12 +71,17 @@ namespace ICSharpCode.AvalonEdit.Folding
 			this.Length = endOffset - startOffset;
 		}
 		
-		internal void Removed()
+		void RemoveCollapsedLineSection()
 		{
 			if (collapsedSection != null) {
-				collapsedSection.Uncollapse();
+				if (collapsedSection.Start != null)
+					collapsedSection.Uncollapse();
 				collapsedSection = null;
 			}
+		}
+		
+		internal void Removed()
+		{
 			manager = null;
 		}
 	}