******* script runtime error *******
type undefined is not an int: (file 'maps/mp/_utility.gsc', line 98)
playfx( level._effect[ self.v[ "fxid" ] ], self.v[ "origin" ], self.v[ "forward" ], self.v[ "up" ] );
*
Error: called from:
(file 'maps/mp/_utility.gsc', line 804)
ent thread cannon_effect();
*
Error: called from:
(file 'maps/mp/_utility.gsc', line 778)
activate_exploder( num );
*
Error: called from:
(file 'maps/mp/_utility.gsc', line 58)
[[ level.exploderFunction ]]( num );
*
Error: called from:
(file 'maps/mp/_load.gsc', line 138)
maps\mp\_utility::exploder( trigger.script_exploder );
*
Error: started from:
(file 'maps/mp/_load.gsc', line 128)
trigger waittill( "trigger" );

The fx entity has the following:
classname/script_model
model/fx
script_exploder/30
script_fxid/wallexplode

This is my mapname.gsc:
main()
{
maps\mp\_load::main();

ambientPlay("ambient_backlot_ext");

game["allies"] = "sas";
game["axis"] = "opfor";
game["attackers"] = "axis";
game["defenders"] = "allies";
game["allies_soldiertype"] = "woodland";
game["axis_soldiertype"] = "woodland";

setdvar( "r_specularcolorscale", "1" );

setdvar("r_glowbloomintensity0",".25");
setdvar("r_glowbloomintensity1",".25");
setdvar("r_glowskybleedintensity0",".3");
setdvar("compassmaxrange","1800");
}

This is my mapname_fx.gsc:

main()
{

level._effect["firelp_med_pm"] = loadfx ("fire/firelp_med_pm_nodistort");
level._effect["firelp_small_pm"] = loadfx ("fire/firelp_small_pm");
level._effect["firelp_small_pm_a"] = loadfx ("fire/firelp_small_pm_a");
level._effect["dust_wind_fast"] = loadfx ("dust/dust_wind_fast");
level._effect["dust_wind_slow"] = loadfx ("dust/dust_wind_slow_yel_loop");
level._effect["dust_wind_spiral"] = loadfx ("dust/dust_spiral_runner");
level._effect["hawk"] = loadfx ("weather/hawk");
level._effect["bird_seagull_flock_large"] = loadfx ("misc/bird_seagull_flock_large");
level._effect["wallexplode"] = loadfx ("explosions\wall_explosion_grnd");

//ambient runners
level._effect[ "mp_overgrown_insects01" ] = loadfx( "ambient_runners/mp_overgrown_insects01" );

/#
if ( getdvar( "clientSideEffects" ) != "1" )
maps\createfx\mp_test_fx::main();
#/


}