Summary:
Currently, MountingCoordinator's RN_SHADOW_TREE_INTROSPECTION code will crash often because it assumes there is always a "new" tree to compare the old tree to. In the LayoutAnimations context this is not always the case - in fact, the majority of the time, LayoutAnimations is producing mutations for animation without a "new" tree.
Just check that the tree exists before trying to print it.
Changelog: [Internal]
Reviewed By: shergin
Differential Revision: D23747289
fbshipit-source-id: a1ba22aeae32ed8915a53bc33cdc199e8ce5128a
Joshua Gross
b64a6618d6