Steps to reproduce:

1. Download the attached project (FillGPUMemory) and open TestScene01
2. Navigate to Assets > Textures and select all render textures within the folder
3. In the Inspector view, change their resolution to 8192x8192
4. Navigate to the Lighting Settings window and bake lighting using the GPU lightmapper
5. Notice that baking stalls, and console spams the following assert:

OpenCL Error: 'clGetProgramInfo(program, CL_PROGRAM_BINARY_SIZES, numDevices * sizeof(size_t), binarySizes.data(), &param_value_size_ret)' returned -44 (CL_INVALID_PROGRAM)!
OpenCL Error. Falling back to CPU lightmapper. Error callback from context: CL_INVALID_PROGRAM

6. Cancel the bake and close the editor
7. Observe the crash

Notes:

- Reproduced on 2018.3.0b5
- Reproduces on nvidia GTX 1080 and AMD R9 Nano Fury
- After setting render texture resolution to 8K, you might need to save the scene and restart the editor