Tolerate null boundingRect in all code paths in DesktopContext#updateDimensions

We had code paths that protected against a null boundingRect,
but not all of them did, which caused crashes if you had
a FocusableNode with a null boundingRect.

Bug: 70768
Change-Id: I92ffdda47626b7638d2c86ad50217b42c45d1acd
Merge "Tolerate null boundingRect in all code paths in DesktopContext#updateDimensions"