fix(ui): bounds-guard out-of-range list access in pop-out and tabs UI

Two pre-existing upstream defects fixed in v1.0.0:

- Ui/Popout.cs PopOutDocked[Idx] now bounds-checks Idx against
  ChatLogWindow.PopOutDocked.Count before reading or writing. A
  popout instance can outlive a list resize when AddPopOutsToDraw()
  rebuilds the docked-state list while a draw frame is in flight,
  which previously produced an out-of-range crash on tab drop
- Ui/SettingsTabs/Tabs.cs guards against an empty worlds list before
  indexing worlds[selectedWorld]. Empty lists can occur briefly when
  switching characters or before the datacenter sheet finishes
  loading — the previous code would crash with an
  ArgumentOutOfRangeException

HellionChat/Ui/Popout.cs

@@ -80,7 +80,10 @@ internal class Popout : Window
         if (!Tab.CanResize)
             Flags |= ImGuiWindowFlags.NoResize;
 
-        if (!ChatLogWindow.PopOutDocked[Idx])
+        // Idx may point past the end if PopOutDocked was resized (e.g., a tab
+        // dropped) between the AddPopOutsToDraw() snapshot and this frame.
+        // Guard the read so we don't index into stale state.
+        if (Idx >= 0 && Idx < ChatLogWindow.PopOutDocked.Count && !ChatLogWindow.PopOutDocked[Idx])
         {
             if (Tab.IndependentOpacity)
             {
@@ -195,6 +198,7 @@ internal class Popout : Window
 
     public override void PostDraw()
     {
+        if (Idx >= 0 && Idx < ChatLogWindow.PopOutDocked.Count)
             ChatLogWindow.PopOutDocked[Idx] = ImGui.IsWindowDocked();
 
         if (Plugin.Config is { OverrideStyle: true, ChosenStyle: not null })

HellionChat/Ui/SettingsTabs/Tabs.cs

@@ -181,6 +181,16 @@ internal sealed class Tabs : ISettingsTab
 
                         ImGui.SameLine();
 
+                        // Guard against an empty worlds list — can happen briefly
+                        // when switching characters or if the datacenter sheet
+                        // has not yet populated. Without the guard the indexed
+                        // access into worlds[selectedWorld] would crash.
+                        if (worlds.Count == 0)
+                        {
+                            ImGui.TextDisabled("(no worlds available)");
+                        }
+                        else
+                        {
                             var selectedWorld = worlds.FindIndex(world => world.RowId == tab.TellTarget.World);
                             if (selectedWorld == -1)
                                 selectedWorld = 0;
@@ -207,6 +217,7 @@ internal sealed class Tabs : ISettingsTab
                                 }
                             }
                         }
+                    }
 
                     var target = (Plugin.TargetManager.SoftTarget ?? Plugin.TargetManager.Target) as IPlayerCharacter;
                     using (ImRaii.Disabled(target == null))