`demoplay` command doesn't work because of NPE

[KvanTTT]

It calls getAverageTreeOwnership with uninitialized rootNode when the tool tries to write the current board state into console.

KataGo/cpp/search/searchresults.cpp

Lines 1749 to 1768 in aa0c53c

	vector<double> Search::getAverageTreeOwnership(const SearchNode* node) const {
	if(node == NULL)
	node = rootNode;
	if(!alwaysIncludeOwnerMap)
	throw StringError("Called Search::getAverageTreeOwnership when alwaysIncludeOwnerMap is false");
	vector<double> vec(nnXLen*nnYLen,0.0);
	auto accumulate = [&vec,this](float* ownership, double selfProp){
	for (int pos = 0; pos < nnXLen*nnYLen; pos++)
	vec[pos] += selfProp * ownership[pos];
	};
	int64_t visits = node->stats.visits.load(std::memory_order_acquire);
	//Stop deepening when we hit a node whose proportion in the final average would be less than this.
	//Sublinear in visits so that the cost of this grows more slowly than overall search depth.
	double minProp = 0.5 / pow(std::max(1.0,(double)visits),0.75);
	//Entirely drop a node with weight less than this
	double pruneProp = minProp * 0.01;
	std::unordered_set<const SearchNode*> graphPath;
	traverseTreeForOwnership(minProp,pruneProp,1.0,node,graphPath,accumulate);
	return vec;
	}

That causes Access violation reading location 0x00000050.