private boolean treeStructureChanged(ProgramModule root1, ProgramModule root2) {
		if (root1 == null) {
			return true;
		}
		return root1.getModificationNumber() != root2.getModificationNumber();
	}
Called when we need to know which tree changed (not enough to know
that the structures are different).
@param root1 root of the original program 
@param root2 root for either the source tree or the destination tree
@return true if there was no original root, OR the modification
numbers for the original tree and tree containing root do not match
Ghidra/Features/Base/src/main/java/ghidra/app/merge/tree/ProgramTreeMergeManager.java