message: core(ocl): Don't query image formats when none exist
  clGetSupportedImageFormats returns CL_INVALID_VALUE if called with
  num_entries 0 and a non-NULL image_formats pointer so let's not do that.
diff: @@ -6445,6 +6445,8 @@ struct Image2D::Impl
  CL_MEM_OBJECT_IMAGE2D, numFormats,
  NULL, &numFormats);
  CV_OCL_DBG_CHECK_RESULT(err, "clGetSupportedImageFormats(CL_MEM_OBJECT_IMAGE2D, NULL)");
  + if (numFormats > 0)
  + {
  AutoBuffer<cl_image_format> formats(numFormats);
  err = clGetSupportedImageFormats(context, CL_MEM_READ_WRITE,
  CL_MEM_OBJECT_IMAGE2D, numFormats,
  @@ -6457,6 +6459,7 @@ struct Image2D::Impl
  return true;
  }
  }
  + }
  return false;
  }
  