TYPO3 Core

If DBAL-Extension is installed the "List users online"-Feature throws this error:

DBAL fatal error: No handler found in handler_getFromTableList() for: "(be_sessions, be_users u) LEFT OUTER JOIN be_users bu ON (ses_backuserid=bu.uid)" (SQL engine parse ERROR: No table name found as expected in parseFromTables()!: near "(be_sessions, be_users u) LEFT OUTER JOIN be_users")

After that, the module is not accessible anymore until the browser-session has been killed by closing the browser.

I removed "LEFT OUTER JOIN" from the SQL-Statement and all works as expected (see attached patch). Is "LEFT OUTER JOIN" really necessary?

I could not install DBAL in 4.2 to reproduce this with latest version, but the sourcecode is similar in 4.2 compared to 4.1.7.
(issue imported from #M8915)