Fix NPE during Editor startup in AutosaveRecovery.java (Fix #10235)

From the original report:
```
*3. Launching problem with OMERO.editor on a Windows system*

OMERO.editor can't be launched. The problem looks similar to this one : http://trac.openmicroscopy.org.uk/ome/ticket/10235
The user really wants to try the application. Any help ?
/Error Log attached to this mail as //_OMERO.editor_Error.log_/
```

/cc @zeb