2.7.2-beta: parameter --opencl-devices is broken
```
xmrig-amd.exe --print-platforms
#0: NVIDIA Corporation
#1: Advanced Micro Devices, Inc.
```
-> openCl platform is 1, OK!

```
xmrig-amd.exe --api-port 3302 -a cryptonight/1 -o stratum+tcp://cryptonightv7.eu.nicehash.com:3363 -u aBcDeFgHiJkL123456789.WorkerName -p x --keepalive --nicehash --donate-level 1 --opencl-platform=1
 * VERSIONS     XMRig/2.7.2-beta libuv/1.22.0 OpenCL/2.0 MSVC/2017
 * CPU          Intel(R) Core(TM) i5-8600K CPU @ 3.60GHz x64 AES
 * ALGO         cryptonight/1, donate=1%
 * POOL #1      stratum+tcp://cryptonightv7.eu.nicehash.com:3363 variant 1
 * API BIND     0.0.0.0:3302
 * COMMANDS     hashrate, pause, resume
[2018-07-16 18:46:54] compiling code and initializing GPUs. This will take a while...
[2018-07-16 18:46:55] found AMD platform index: 1, name: Advanced Micro Devices, Inc.
[2018-07-16 18:46:55] found OpenCL GPU: Radeon (TM) RX 470 Graphics, cu: 32
[2018-07-16 18:46:55] found OpenCL GPU: AMD Radeon (TM) RX 560, cu: 16
[2018-07-16 18:46:55] #0, GPU #0 Radeon (TM) RX 470 Graphics, intensity: 768 (8/256), cu: 32
[2018-07-16 18:46:55] #1, GPU #1 AMD Radeon (TM) RX 560, intensity: 768 (8/256), cu: 16
[2018-07-16 18:46:56] use pool cryptonightv7.eu.nicehash.com:3363 169.51.33.3
[2018-07-16 18:46:56] new job from cryptonightv7.eu.nicehash.com:3363 diff 100001 algo cn/1
^C
```
Without --opencl-devices it is working OK!

```
xmrig-amd.exe --api-port 3302 -a cryptonight/1 -o stratum+tcp://cryptonightv7.eu.nicehash.com:3363 -u aBcDeFgHiJkL123456789.WorkerName -p x --keepalive --nicehash --donate-level 1 --opencl-platform=1 --opencl-devices=0
 * VERSIONS     XMRig/2.7.2-beta libuv/1.22.0 OpenCL/2.0 MSVC/2017
 * CPU          Intel(R) Core(TM) i5-8600K CPU @ 3.60GHz x64 AES
 * ALGO         cryptonight/1, donate=1%
 * POOL #1      stratum+tcp://cryptonightv7.eu.nicehash.com:3363 variant 1
 * API BIND     0.0.0.0:3302
 * COMMANDS     hashrate, pause, resume
[2018-07-16 18:47:10] compiling code and initializing GPUs. This will take a while...
[2018-07-16 18:47:10] #0, GPU #0 Radeon (TM) RX 470 Graphics, intensity: 0 (8/256), cu: 32
[2018-07-16 18:47:11] Error CL_INVALID_BUFFER_SIZE when calling clCreateBuffer to create hash scratchpads buffer.
[2018-07-16 18:47:11] Failed to start threads
```
Same error with --opencl-devices=1, or even --opencl-devices=0,1

This is with blockchain drivers.