message: Only include placeholder in DOM when necessary
diff: @@ -276,8 +276,8 @@ export default class extends React.Component {
  { /* Calculate aspect ratio, using %padding will size _container correctly */ }
  <div style={{ paddingBottom: (100 * content.info.h / content.info.w) + '%' }}></div>
  + { showPlaceholder &&
  <div className="mx_MImageBody_thumbnail" style={{
  - "display": showPlaceholder ? undefined : 'none',
  // Constrain width here so that spinner appears central to the loaded thumbnail
  "max-width": content.info.w + "px",
  }}>
  @@ -285,6 +285,7 @@ export default class extends React.Component {
  { placeholder }
  </div>
  </div>
  + }
  <div style={{display: !showPlaceholder ? undefined : 'none'}}>
  { img }
  