Check existence of node during expand/collapse before acting on it

[jej2003]

update handling of expanding/collapsing nodes to ensure they exist in the tree

addresses #191

[dgreene1]

@mellis481, @yhy-1 do either of you have capacity to review this?

@jej2003 if it doesn’t have unit tests, can you add one?

[jej2003]

@dgreene1 i will look to add one today. Is there a good starting point you could recommend? If not I’ll see if anything exists to base it on

[jej2003]

@dgreene1 , take a look at the updated changes with tests. Any feedback would be appreciated, thanks!

[jej2003]

Philosophically do we want the implementation to be capable of handling data being passed to expandedIds/selectedIds that may not exist in the tree or do we still want to throw in those situations? The changes I implemented and as are demonstrated in the tests make it so that if any ids in expandedIds/selectedIds don't exist the tree will not crash. Conversely, if we want that to still happen then I believe a smaller change is possible. Alternative approach is available at https://github.com/dgreene1/react-accessible-treeview/pull/217/files