message: fix a floating-point exception when the viewport is too small
  this could lead to w/h froxel count to be 0, later leading to
  divide-by-zero. There could also be a case where the viewport itself
  had w/h of zero, also leading to divide-by-zero exception.
diff: @@ -206,6 +206,9 @@ void Froxelizer::computeFroxelLayout(
  filament::Viewport const& viewport) noexcept {
  if (SUPPORTS_NON_SQUARE_FROXELS == false) {
  + const uint32_t width = std::max(16u, viewport.width);
  + const uint32_t height = std::max(16u, viewport.height);
  +
  // calculate froxel dimension from FROXEL_BUFFER_ENTRY_COUNT_MAX and viewport
  // - Start from the maximum number of froxels we can use in the x-y plane
  size_t froxelSliceCount = FEngine::CONFIG_FROXEL_SLICE_COUNT;
  @@ -213,18 +216,22 @@ void Froxelizer::computeFroxelLayout(
  // - compute the number of square froxels we need in width and height, rounded down
  // solving: | froxelCountX * froxelCountY == froxelPlaneCount
  // | froxelCountX / froxelCountY == width / height
  - size_t froxelCountX = size_t(std::sqrt(froxelPlaneCount * viewport.width / viewport.height));
  - size_t froxelCountY = size_t(std::sqrt(froxelPlaneCount * viewport.height / viewport.width));
  + size_t froxelCountX = size_t(std::sqrt(froxelPlaneCount * width / height));
  + size_t froxelCountY = size_t(std::sqrt(froxelPlaneCount * height / width));
  // - copmute the froxels dimensions, rounded up
  - size_t froxelSizeX = (viewport.width + froxelCountX - 1) / froxelCountX;
  - size_t froxelSizeY = (viewport.height + froxelCountY - 1) / froxelCountY;
  + size_t froxelSizeX = (width + froxelCountX - 1) / froxelCountX;
  + size_t froxelSizeY = (height + froxelCountY - 1) / froxelCountY;
  // - and since our froxels must be square, only keep the largest dimension
  size_t froxelDimension = std::max(froxelSizeX, froxelSizeY);
  // Here we recompute the froxel counts which may have changed a little due to the rounding
  // and the squareness requirement of froxels
  - froxelCountX = (viewport.width + froxelDimension - 1) / froxelDimension;
  - froxelCountY = (viewport.height + froxelDimension - 1) / froxelDimension;
  + froxelCountX = (width + froxelDimension - 1) / froxelDimension;
  + froxelCountY = (height + froxelDimension - 1) / froxelDimension;
  +
  + assert(froxelCountX);
  + assert(froxelCountY);
  + assert(froxelCountX * froxelCountY <= froxelPlaneCount);
  *dim = froxelDimension;
  *countX = uint16_t(froxelCountX);
  