message: fix room lists growing taller than screen height in FF
  sections with flex-basis don't seem to shrink smaller in FF,
  so use flexGrow which is unitless/proportional but works as well
diff: @@ -350,7 +350,7 @@ const RoomSubList = React.createClass({
  } else {
  const heightEstimation = (len * 40) + 31;
  const style = {
  - flexBasis: `${heightEstimation}px`,
  + flexGrow: `${heightEstimation}`,
  maxHeight: `${heightEstimation}px`,
  };
  const GeminiScrollbarWrapper = sdk.getComponent("elements.GeminiScrollbarWrapper");
  