I learned that get_user_origin() returns the origin in integers, but an entity must be spawned at a float.. here is the working code.
Code:
public create_function(id, level, cid)
{
if(!cmd_access(id, level, cid, 1))
return PLUGIN_HANDLED
new Float:float_origin[3]
new integer_origin[3]
get_user_origin(id, integer_origin, 3)
for(new i = 0; i < 3; i++)
float_origin[i] = float(integer_origin[i])
new ent = create_entity("info_target")
entity_set_string(ent,EV_SZ_classname,"stupok69_ent")
entity_set_model(ent,MODEL)
entity_set_origin(ent,float_origin)
return PLUGIN_HANDLED
}