Fix duplicated image node when updateing already inserted image. [5.1.x]

[petschki]

fixes plone/Products.CMFPlone#3910

[pbauer]

How do I test that? I forgot how to get Plone to use the raw js instead of the minified bundle.

[petschki]

1. checkout mockup
2. run yarn install && yarn start:webpack inside the package
3. in the resource controlpanel go to the plone bundle and use http://localhost:8000/bundle.min.js as javascript resource

[pbauer]

I tested plone/plone.staticresources#323 with 6.1 and it worked.

yarn start:webpack did not work:

mockup git:(5.1.x) $ yarn start:webpack
command not found: webpack`

[petschki]

yarn start:webpack did not work:

hm ... strange. maybe this is because of yarn version ... mockup only runs in yarn < 2

I'll prepare releases now for the fix.