Fix polyobject and SPB 'lastlook' interaction crash

Fixes an interaction with SPBs "standing" on Polyobjects being given a huge number on their lastlook variable. Players who were to die while the SPB "stands" on a polyobject (which would have the SPB switch to its wait behaviour and check this variable) would cause the server/all clients in the server to crash.

This is more of a bandaid solution, ideally SPBs should be using something else rather than lastlook to store the player to track after death, but this way there are no breaking changes with addons that happen to interact with that variable.

First merge request. :)