Handle two UI misbehaviors

Hover tooltip thread was throwing exceptions (silently, cuz thread); program starts with empty box slots, hovering between them would never show -> can't hide a never-shown (no handle) form
Fix quirk with stat ordering and visibility toggling

PKHeX.WinForms/Controls/PKM Editor/StatEditor.cs

@@ -615,6 +615,12 @@ private void SetStatOrder(StatEditorStatOrder order)
         if (order == StatOrder)
             return;
 
+        // https://stackoverflow.com/a/30219698
+        // WinForms hack to create the handles and avoid Z-order changing on visibility toggle.
+        // Otherwise, our stat ordering may be incorrect if we change it more than once.
+        foreach (Control ctrl in FLP_Stats.Controls)
+            _ = ctrl.Handle;
+
         // In Generation 1, Special Defense and Special Attack are combined.
         // Additionally, Speed is shown before Special.
         const int baseIndex = 1;

PKHeX.WinForms/Controls/Slots/SummaryPreviewer.cs

@@ -68,6 +68,10 @@ public void Clear()
         var src = _source;
         Task.Run(async () =>
         {
+            if (!Previewer.IsHandleCreated)
+                return; // not shown ever
+
+            // Give a little bit of fade-out delay
             await Task.Delay(50, CancellationToken.None).ConfigureAwait(false);
             if (!src.IsCancellationRequested)
                 Previewer.Invoke(Previewer.Hide);