Problem Page can”t be edited after wordpress update

Hello,

after updating to the new wordpress, some of my pages cannot be edited anymore…(really weird)
OK I did a few updates (…) But it didn’t change the problem.
So I activated the debug mode to true to this the error message which was not displaying.

It is weird because I can still edit lots of page but just a few of pages cannot be edited and the page gets white (since I updated to the last wordpress version)

Here is the error message displaying
Notice: Undefined index: extended_valid_elements in /wp-content/plugins/protect-schemaorg-markup-in-html-editor/tinymce-schemaorg-markup.php on line 64

So it is because of this plugin

maybe deactivating it could solve my problem when I have to edit my page and then I should activate it again once I am done ) ?

Thanks.