Upgrade from 5.2.2 to 5.4 M1 is broken

Steps to reproduce:

1. unpack xwiki-enterprise-jetty-hsqldb-5.2.2
2. start the wiki, look if all looks ok.
3. stop the wiki
4. replace webapp/xwiki with the webapp of 5.4M1 or the last snapshot
5. remove data/solr to avoid problems
6. enabled snapshot extensions repository in xwiki.properties
7. start the wiki
8. when DW is lauched, upgrade the main wiki

Then the wiki seems empty (see screenshot).