clear the command buffer when changing focus away from it

src/gui/Window.cc

@@ -293,6 +293,7 @@ void Window::handle_keyval(uint32_t keyval)
             {
                 if (m_focused_buffer_pane == m_command_buffer_pane)
                 {
+                    m_command_buffer_pane->clear();
                     change_focus(m_buffer_pane);
                 }
                 else