Description
Due to a problem in the Quartus® II software version 13.0 SP1 and earlier, you may encounter this internal error when closing a project. This error can occur if you have used the load_report Tcl command and not used the unload_report command when done processing the report.
Resolution
To avoid this issue, always issue the unload_report Tcl command after processing of the report file.
This problem is scheduled to be fixed in a future release of the Quartus II software.