JSOC RHS Radio Fix

a placard slot (e.g. an SC4200EP on a JPC radio placard), the preview entity is destroyed before the radio's deferred Register() call runs. The dead call stays stuck in the call queue and throws a script exception every cycle from then on — silently dropping the affected player's FPS (often to ~25) until they reconnect.
This mod adds a small script patch to 
always removes the queued Register() call when the entity is deleted (the original only does this server-side)
guards Register() against running with a null owner
No content, no assets, no gameplay changes — pure bug fix, a few KB. Works on all platforms including console. Safe to add to any server running RHS; clients load it automatically from the server's mod list.
Requires: RHS – Status Quo (+ Content Pack 01 & 02)
All credit for the Spectrum Device / radio systems to the RHS team — this is a temporary community patch until the fix lands upstream, and can be removed once it does.