(bug): 'TypeError: Cannot read property 'classList' of null' when adding an image to a blog

Sentry Issue: FRONT-10

TypeError: Cannot read property 'classList' of null
  at l.positionButtons (/front/dist/en/main.8bc7038e8a75ccb149b3.js:1:2569378)
  at r (/front/dist/en/vendor.8d69333b6d98bfb0c648.js:1:150690)
  at e.invokeTask (/front/dist/en/polyfills.a53d7f14fce4c9ab2f16.js:1:7985)
  at Object.onInvokeTask (/front/dist/en/vendor.8d69333b6d98bfb0c648.js:1:3624171)
  at e.invokeTask (/front/dist/en/polyfills.a53d7f14fce4c9ab2f16.js:1:7906)
...
(4 additional frame(s) were not displayed)