fix: empty command-palette filter no longer crashes the TUI render (issue #26)

lib/bds/tui.ex

@@ -487,7 +487,7 @@ defmodule BDS.TUI do
     [
       {%List{
          items: items,
-         selected: state.selected,
+         selected: list_selected(items, state.selected),
          highlight_style:
            if(focused?,
              do: %Style{fg: :black, bg: :cyan},
@@ -498,6 +498,11 @@ defmodule BDS.TUI do
     ]
   end
 
+  # The List widget requires selected: nil when the collection is empty
+  # and raises otherwise — clamp every dynamic list through this.
+  defp list_selected([], _selected), do: nil
+  defp list_selected(items, selected), do: min(selected, length(items) - 1)
+
   defp main_widgets(%{editor: nil} = state, rect) do
     text =
       case selected_item(state) do
@@ -621,7 +626,7 @@ defmodule BDS.TUI do
       {%Clear{}, overlay},
       {%List{
          items: items,
-         selected: if(command.help?, do: nil, else: command.selected),
+         selected: if(command.help?, do: nil, else: list_selected(items, command.selected)),
          highlight_style: %Style{fg: :black, bg: :cyan},
          block: %Block{title: title, borders: [:all]}
        }, overlay}
@@ -642,7 +647,7 @@ defmodule BDS.TUI do
       {%Clear{}, overlay},
       {%List{
          items: report_lines(report),
-         selected: report.scroll,
+         selected: list_selected(report_lines(report), report.scroll),
          scroll_padding: 2,
          highlight_style: %Style{modifiers: [:bold]},
          block: %Block{title: report_title(report), borders: [:all]}

test/bds/tui_test.exs

@@ -230,6 +230,15 @@ defmodule BDS.TUITest do
       assert is_binary(action)
     end
 
+    test "input that matches no command renders without errors" do
+      state = mount_with_executor!() |> press(":") |> press("j")
+
+      # Filtering down to zero commands must not blow up the render
+      # (List panics on a selected index into an empty item list).
+      text = screen_text(state)
+      assert text =~ ":j"
+    end
+
     test "no match reports an unknown command" do
       state =
         mount_with_executor!()