fix effect_set_category

libeffect.cpp

@@ -271,8 +271,11 @@ int32_t scriptlib::effect_set_category(lua_State *L) {
 	check_param_count(L, 2);
 	check_param(L, PARAM_TYPE_EFFECT, 1);
 	effect* peffect = *(effect**) lua_touserdata(L, 1);
-	uint32_t v = (uint32_t)lua_tointeger(L, 2);
-	peffect->category = v;
+	int64_t v = lua_tointeger(L, 2);
+	if(v < 0) {
+		return luaL_error(L, "Parameter 2 should be non-negative.");
+	}
+	peffect->category = (uint64_t)v;
 	return 0;
 }
 int32_t scriptlib::effect_set_hint_timing(lua_State *L) {