Right now handleCommand returns a boolean. However, as I modified settings, I realized there may well be three cases:
The third one doesn't quite overlap with false; false works in that the global handler will try to do something, but doesn't in that the error message should be from the specific screen if the global one can't handle something.
In particular, the settings screen is a good example - if the users says they want to change a setting, it is expected that they are going to enter a value for that new setting, but they could decide they want to bail instead. With the true/false dichotomy, we can't both show a sensible error message and let them bail out.