Fix LT-22018: Typing lost in example and translation fields

Src/Common/Controls/DetailControls/DataTree.cs

@@ -154,6 +154,7 @@ public class DataTree : UserControl, IVwNotifyChange, IxCoreColleague, IRefresha
 		bool m_fDoNotRefresh = false;
 		bool m_fPostponedClearAllSlices = false;
 		// Set during ConstructSlices, to suppress certain behaviors not safe at this point.
+		bool m_postponePropChanged = true;
 		internal bool ConstructingSlices { get; private set; }
 
 		public List<Slice> Slices { get; private set; }
@@ -527,6 +528,15 @@ public LcmStyleSheet StyleSheet
 
 		}
 
+		public virtual bool OnPostponePropChanged(object commandObject)
+		{
+			if ((bool)commandObject == true)
+				m_postponePropChanged = true;
+			else
+				m_postponePropChanged = false;
+			return true;
+		}
+
 		public void PropChanged(int hvo, int tag, int ivMin, int cvIns, int cvDel)
 		{
 			CheckDisposed();
@@ -557,7 +567,13 @@ public void PropChanged(int hvo, int tag, int ivMin, int cvIns, int cvDel)
 				// because some slice data structures that are being used by the invoker
 				// get disposed by RefreshList (LT-21980, LT-22011).  So we postpone calling
 				// RefreshList until the work is done.
-				this.BeginInvoke(new Action(PostponedRefreshList));
+				if (m_postponePropChanged)
+				{
+					this.BeginInvoke(new Action(RefreshListAndFocus));
+				} else
+				{
+					RefreshListAndFocus();
+				}
 			}
 			// Note, in LinguaLinks import we don't have an action handler when we hit this.
 			else if (m_cache.DomainDataByFlid.GetActionHandler() != null && m_cache.DomainDataByFlid.GetActionHandler().IsUndoOrRedoInProgress)
@@ -584,7 +600,7 @@ public void PropChanged(int hvo, int tag, int ivMin, int cvIns, int cvDel)
 			}
 		}
 
-		private void PostponedRefreshList()
+		private void RefreshListAndFocus()
 		{
 			if (!IsDisposed)
 			{

Src/Common/Controls/DetailControls/GhostStringSlice.cs

@@ -454,7 +454,19 @@ private void SwitchToReal()
 				// Make the real object and set the string property we are ghosting. The final PropChanged
 				// will typically dispose this and create a new string slice whose key is our own key
 				// followed by the flid of the string property.
-				int hvoNewObj = MakeRealObject(tssTyped);
+				// To avoid problems, PropChanged must not be postponed (cf. LT-22018).
+				// Copy m_mediator in case 'this' gets disposed.
+				Mediator mediator = m_mediator;
+				int hvoNewObj;
+				try
+				{
+					mediator.SendMessage("PostponePropChanged", false);
+					hvoNewObj = MakeRealObject(tssTyped);
+				}
+				finally
+				{
+					mediator.SendMessage("PostponePropChanged", true);
+				}
 
 				// Now try to make a suitable selection in the slice that replaces this.
 				RestoreSelection(ich, datatree, parentKey, hvoNewObj, flidStringProp, wsToCreate);