Implements a patch for bug 2964527, "Problems with multiple breakpoints in operation chain". When displaying a breakpoint we switch to the corresponding TransformationPage automatically. If, at that point, another TransformationPage is already open, and it has its Formula Builder open, we must close that Formula Builder first.
Note that switching to another TransformationPage manually is not possible in this situation, since the Formula Builder is modal, so it blocks the rest of the UI.