fix Tree initialization

[GGAutomaton]

Initializes the Tree::_size member to 0.

This fixes a bug where an uninitialized _size would cause size checks in connectInTrees and connectOutTrees to fail, preventing the trees from connecting.

program-dependence-graph/src/ProgramDependencyGraph.cpp

Lines 84 to 87 in 8632566

	void pdg::ProgramDependencyGraph::connectInTrees(Tree *src_tree, Tree *dstTree, EdgeType edgeTy)
	{
	if (src_tree->size() != dstTree->size())
	return;

Note: This bug likely affects other active branches.