message: Avoid a reflow when setting caret position on an empty composer
  This saves an extra ~12 ms on each room switch, because we can.
diff: @@ -43,6 +43,8 @@ function setDocumentRangeSelection(editor: HTMLDivElement, model: EditorModel, r
  }
  export function setCaretPosition(editor: HTMLDivElement, model: EditorModel, caretPosition: IPosition) {
  + if (model.isEmpty) return; // selection can't possibly be wrong, so avoid a reflow
  +
  const range = document.createRange();
  const { node, offset } = getNodeAndOffsetForPosition(editor, model, caretPosition);
  range.setStart(node, offset);
  