message: Group.css: fixed background for .Group__inner in card mode
diff: }
  .Group--card > .Group__inner {
  - background: var(--modal_card_background);
  + background: var(--background_content);
  border-radius: 8px;
  box-shadow: inset 0 0 0 var(--thin-border) var(--input_border);
  }
  