Release display buffers when a window is added to free list

src/client_manager.cc

@@ -98,6 +98,7 @@ WindowAndSelections ClientManager::get_free_window(Buffer& buffer)
 
 void ClientManager::add_free_window(std::unique_ptr<Window>&& window, SelectionList selections)
 {
+    window->clear_display_buffer();
     Buffer& buffer = window->buffer();
     m_free_windows.push_back({ std::move(window), SelectionList{ std::move(selections) }, buffer.timestamp() });
 }

src/window.hh

@@ -42,6 +42,8 @@ public:
 
     ByteCoord offset_coord(ByteCoord coord, CharCount offset);
     ByteCoordAndTarget offset_coord(ByteCoordAndTarget coord, LineCount offset);
+
+    void clear_display_buffer() { m_display_buffer = DisplayBuffer{}; }
 private:
     Window(const Window&) = delete;