Lazy-loading collection now only increases its version when the total item count changes

Source/Collections/AsyncVirtualObservableReadOnlyList.cs

@@ -811,12 +811,14 @@ namespace Nuclex.Avalonia.Collections {
           if(fetchedItemCount < this.pageSize) {
             itemCount = offset + fetchedItemCount;
             lock(this) {
+              if(itemCount < this.assumedCount) {
                 this.assumedCount = itemCount;
-            }
 #if DEBUG
                 ++this.version;
 #endif
               }
+            }
+          }
 
           // The count may have been adjusted if this truncated the list,
           // so recalculate the actual number of items. Then send out change