message: Add mount-guards to MImageBody
diff: /*
  Copyright 2015, 2016 OpenMarket Ltd
  Copyright 2018 New Vector Ltd
  -Copyright 2018 Michael Telatynski <7t3chguy@gmail.com>
  +Copyright 2018, 2019 Michael Telatynski <7t3chguy@gmail.com>
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  @@ -264,6 +264,7 @@ export default class MImageBody extends React.Component {
  decryptedBlob = blob;
  return URL.createObjectURL(blob);
  }).then((contentUrl) => {
  + if (this.unmounted) return;
  this.setState({
  decryptedUrl: contentUrl,
  decryptedThumbnailUrl: thumbnailUrl,
  @@ -271,6 +272,7 @@ export default class MImageBody extends React.Component {
  });
  });
  }).catch((err) => {
  + if (this.unmounted) return;
  console.warn("Unable to decrypt attachment: ", err);
  // Set a placeholder image when we can't decrypt the image.
  this.setState({
  