private int[] lastBlockLightValue;

    private void setCurrentBlockLightValues()
    {
        for(int lx = -1; lx <= 1; lx++)
        {
            for(int ly = -1; ly <= 1; ly++)
            {
                for(int lz = -1; lz <= 1; lz++)
                {
                    if(worldObj.getBlockId((int)posX + lx, (int)posY + ly, (int)posZ + lz) != 0) continue;
                    int lux = 13;
                    if(lx == 0 && ly == 0 && lz == 0)
                    {
                        lux = 15;
                    }
                    else if(lx == 0 || ly == 0 || lz == 0)
                    {
                        lux = 14;
                    }
                    worldObj.setLightValue(EnumSkyBlock.Block, (int)posX + lx, (int)posY + ly, (int)posZ + lz, lux);
                }
            }
        }
    }

    private void restoreLastBlockLightValues()
    {
        for(int lx = -1; lx <= 1; lx++)
        {
            for(int ly = -1; ly <= 1; ly++)
            {
                for(int lz = -1; lz <= 1; lz++)
                {
                    if(worldObj.getBlockId((int)lastTickPosX + lx, (int)lastTickPosY + ly, (int)lastTickPosZ + lz) != 0) continue;
                    worldObj.setLightValue(EnumSkyBlock.Block, (int)lastTickPosX + lx, (int)lastTickPosY + ly, (int)lastTickPosZ + lz, lastBlockLightValue[(lz+1)*9+(ly+1)*3+(lx+1)]);
                }
            }
        }
    }

    private void storeCurrentBlockLightValues()
    {
        for(int lx = -1; lx <= 1; lx++)
        {
            for(int ly = -1; ly <= 1; ly++)
            {
                for(int lz = -1; lz <= 1; lz++)
                {
                    if(worldObj.getBlockId((int)posX + lx, (int)posY + ly, (int)posZ + lz) != 0) continue;
                    lastBlockLightValue[(lz+1)*9+(ly+1)*3+(lx+1)] = worldObj.getBlockLightValue((int)posX + lx, (int)posY + ly, (int)posZ + lz);
                }
            }
        }
    }

    public void setEntityDead()
    {
        isDead = true;
        restoreLastBlockLightValues();
    }

In the Entity's constructor:

        lastBlockLightValue = new int[27];
        storeCurrentBlockLightValues();
    setCurrentBlockLightValues();

In the Entity's onUpdate function:

        if((int)posX != (int)lastTickPosX || (int)posY != (int)lastTickPosY || (int)posZ != (int)lastTickPosZ)
        {
            restoreLastBlockLightValues();
            storeCurrentBlockLightValues();
            setCurrentBlockLightValues();
        }