Kill Spectator PFEH when exiting spectator

Should fix #2989
There is a race condition between these 4 PFEH and the "onUnload" event
in handleInterface.
If the PFEHs run first they will use nil variables and throw a script
error.
This sets them to nil immediately when exiting spectator

addons/spectator/functions/fnc_setSpectator.sqf

@@ -127,6 +127,12 @@ if (_set) then {
     GVAR(unitCamera) = nil;
     GVAR(targetCamera) = nil;
 
+    //Kill these PFEH handlers now because the PFEH can run before the `onunload` event is handled
+    GVAR(camHandler) = nil;
+    GVAR(compHandler) = nil;
+    GVAR(iconHandler) = nil;
+    GVAR(toolHandler) = nil;
+
     // Cleanup display variables
     GVAR(ctrlKey) = nil;
     GVAR(heldKeys) = nil;