squeak: must fail bitblt if source form is invalid
squeak: must fail bitblt if source form is invalid

LivelyKernel/LivelyKernel,NikolaySuslov/LivelyKernel,pascience/LivelyKernel,LivelyKernel/LivelyKernel,LivelyKernel/LivelyKernel,NikolaySuslov/LivelyKernel,pascience/LivelyKernel,NikolaySuslov/LivelyKernel,pascience/LivelyKernel