Fix the weirdest combobox bug

If you don't set Handled to true in the handler, the SelectionChanged event bubbles up to the parent TabControl and resets the entire graph recreating the entire tab.

Author: KirillOsenkov

src/StructuredLogViewer/Controls/BuildControl.xaml.cs

@@ -540,6 +540,11 @@ private void CentralTabControl_SelectionChanged(object sender, SelectionChangedE
 
         private void PopulateProjectReferenceGraph()
         {
+            if (projectReferenceGraphTab.Content is GraphHostControl)
+            {
+                return;
+            }
+
             var graph = Build.ProjectReferenceGraph.Graph;
 
             var graphHostControl = new GraphHostControl();

src/StructuredLogViewer/Controls/GraphHostControl.cs

@@ -336,6 +336,7 @@ private void Initialize()
 
         filterModeComboBox.SelectionChanged += (s, e) =>
         {
+            e.Handled = true;
             graphControl.FilterMode = filterModeComboBox.SelectedIndex switch
             {
                 0 => GraphFilterMode.None,