Found it!
Actually svg plugin calls an XML function “simplexml_load_file()” when you click on Grid View in the Media Manager. This function seems to come naturally with PHP5 but not naturally at all with PHP7! Therefore its package has to be installed manually:
apt-get install php7.0-xml
Then you relaunch your web server, and then the grid view works with svg-plugin AND PHP7!
Have a nice day!
