Insert into Basic.java (or whatever you called it)

    public static final StepSound soundGrassFootstep2 = new StepSound("grass", 1.0F, 1.0F);
    public final static Block genericLeaves = new GenericLeavesBlock(502) // , Material.leaves, true)
        .setCreativeTab(CreativeTabs.tabBlock).setTextureName(BasicInfo.NAME.toLowerCase() + ":GenericLeaves")
        .setLightOpacity(1).setStepSound(soundGrassFootstep2).setUnlocalizedName("genericLeaves")
        .setHardness(0.2F).setLightValue(1.0f);