UEditorEngine::AddPendingLateJoinClient checks original PIE/SIE state, not current state

When adding late joining clients, the engine checks the originally requested EPlaySessionWorldType, rather than checking whether or not the session is currently simulating or not.
This means if the editor session started as simulating and was switched to PIE, attempting to add a new client will result in the following ensure: "RequestLateJoin shouldn't be called for SIE!"
Conversely, if the editor session started as PIE and was switched to SIE, clients can be added without any error messages.

In the editor, enable "Allow late joining" under Editor Preferences -> General -> Experimental.
Start a "Simulate In Editor" session.
Switch to PIE by using F8 or the toolbar button.
Once in PIE, use the toolbar button to attempt to add another client.