Hi @Lionel_Scheepmans, thanks for taking the time to report this!

If I go to https://fr.wikiversity.org/wiki/Recherche:Imagine_un_monde/Innovations?veaction=edit&debug=true and open the web browser's developer tools and look at the console, it shows the error TypeError: href is null.
See https://www.mediawiki.org/wiki/Help:Locating_broken_scripts for more information how to use the developer tools of your browser to find such problems yourself.

TypeError: href is null ve.dm.MWInternalLinkAnnotation.js:141:2
    getTargetDataFromHref https://fr.wikiversity.org/w/extensions/VisualEditor/modules/ve-mw/dm/annotations/ve.dm.MWInternalLinkAnnotation.js?14f21:141
    toDataElement https://fr.wikiversity.org/w/extensions/VisualEditor/modules/ve-mw/dm/nodes/ve.dm.MWBlockImageNode.js?be379:89
    createDataElements https://fr.wikiversity.org/w/extensions/VisualEditor/lib/ve/src/dm/ve.dm.Converter.js?38061:545
    getDataFromDomSubtree https://fr.wikiversity.org/w/extensions/VisualEditor/lib/ve/src/dm/ve.dm.Converter.js?38061:848
    getModelFromDom https://fr.wikiversity.org/w/extensions/VisualEditor/lib/ve/src/dm/ve.dm.Converter.js?38061:619
    createModelFromDom https://fr.wikiversity.org/w/extensions/VisualEditor/lib/ve/src/init/ve.init.Target.js?a0674:232
    createModelFromDom https://fr.wikiversity.org/w/extensions/VisualEditor/modules/ve-mw/init/targets/ve.init.mw.Target.js?fad3e:182
    setupSurface https://fr.wikiversity.org/w/extensions/VisualEditor/modules/ve-mw/init/targets/ve.init.mw.Target.js?fad3e:373

Change 543956 had a related patch set uploaded (by Bartosz Dziewoński; owner: Bartosz Dziewoński):
[mediawiki/extensions/VisualEditor@master] Fix media embeds which don't link to the file page

https://gerrit.wikimedia.org/r/543956

Thanks a lot for all this information and explanations. I gone try to understand all of that latter and I'll be back after few test trying to locate or fix the bug. Cheers,

Change 543956 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] Fix media embeds which don't link to the file page

https://gerrit.wikimedia.org/r/543956

In T235707#5585057, @matmarex wrote:

This is apparently triggered by the video embed on that page. I made a mistake in my fix for T193253: I assumed that a media thumbnail would always be a link to its description page, but this is not the case for videos. Syntax for images like [[File:Example.jpg|link=]] would also trigger the bug.

Ok, I've removed the two videos of the page and the Visual Editor run again.
Now they are on my draft page (https://fr.wikiversity.org/wiki/Utilisateur:Lionel_Scheepmans/Brouillon) where the bug is now present.

So my question now is : how can I integrate video in my work ?
Is that some thing than I can deal with or is that a bug on the visual editro side than I can do nothing ?

Other information mayebe useful : the visual editor have no bug on wikicode edition (new wikitext mode) even when video are still on the page.

So my question now is : how can I integrate video in my work ?

By waiting a few days. :) MatmaRex' software change ("patch") to fix the problem has been merged into the code repository (see T235707#5586291). The code in the code repository will be put ("deployed") onto French Wikiversity servers on Wed 23rd of October. So the problem here should not happen anymore after that day.

In T235707#5588651, @Aklapper wrote:

So my question now is : how can I integrate video in my work ?

By waiting a few days. :) MatmaRex' software change ("patch") to fix the problem has been merged into the code repository (see T235707#5586291). The code in the code repository will be put ("deployed") onto French Wikiversity servers on Wed 23rd of October. So the problem here should not happen anymore after that day.

Ok, @Aklapper and thanks for this information. I can wait. No problem. Have a nice day !

Change 545230 had a related patch set uploaded (by Bartosz Dziewoński; owner: Bartosz Dziewoński):
[mediawiki/extensions/VisualEditor@wmf/1.35.0-wmf.2] Fix media embeds which don't link to the file page

https://gerrit.wikimedia.org/r/545230

Two bug reports is a lot, so I'm making a guess that many people are running into this. I'll have the patch deployed early (now).

Change 545230 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@wmf/1.35.0-wmf.2] Fix media embeds which don't link to the file page

https://gerrit.wikimedia.org/r/545230

Mentioned in SAL (#wikimedia-operations) [2019-10-22T11:28:20Z] <urbanecm@deploy1001> Synchronized php-1.35.0-wmf.2/extensions/VisualEditor/: SWAT: rEVED2bc4420c1963 (T235707); rEVED680a98b89294 (T233320); rEVEDd83265dd0a20 (T234564) (duration: 00m 53s)

This should be resolved on all Wikimedia wikis now.

This seems to be working for me.