Update to fix crashing when installing modules

The webui client was crashing when installing a new module with: 
"PHP Fatal error:  Cannot pass parameter 1 by reference in /usr/share/phoronix-test-suite/pts-core/objects/client/display_modes/pts_websocket_display_mode.php on line 196"
This is because update_install_status was trying to pass the reference of 'null', and PHP hates that.
I have updated it to create a temp variable set to 'null' and then pass that in.