Fix LT-20337: Crash Navigating From Bulk Edit Phoneme Features (#426)

Author: jtmaxwell3

Src/LexText/LexTextControls/PhonologicalFeaturePopupTreeManager.cs

@@ -221,9 +221,12 @@ protected override void Dispose(bool disposing)
 				{
 					Cache.DomainDataByFlid.BeginUndoTask(LexTextControls.ksUndoInsertPhonologicalFeature,
 									 LexTextControls.ksRedoInsertPhonologicalFeature);
-					foreach (var cmBaseAnnotation in m_annotations)
+					foreach (var cmBaseAnnotation in m_annotations.ToList())
 					{
-						cmBaseAnnotation.Delete();
+						if (cmBaseAnnotation.IsValidObject)
+							cmBaseAnnotation.Delete();
+						else
+							m_annotations.Remove(cmBaseAnnotation);
 					}
 					Cache.DomainDataByFlid.EndUndoTask();
 				}