The `width` passed to `SurfaceImpl::DrawRGBAImage` is 0 (probably due to marking a zero-width character) so the bitmap vector size is 0. It is calling `std::vector::operator[0]` which is out-of-bounds but shouldn't be checked or cause a failure.
Add a check for empty size at the top of `SurfaceImpl::DrawRGBAImage` and it will likely be happy.