Cannot delete number in second time signature box with one digit

1. New.
2. At the time signature step, click to the right of the number in the second box.
3. Delete.

Result: It doesn't delete, unless there's two digits.

Workaround: Drag-select the digit and enter the number.

Discussion: Also applicable in 'Measure Properties'. The number in the first box can be deleted (until you click elsewhere, in which the number is reinstated). I report this because in some situations, it might be difficult to change the number in the second box.

Using MuseScore 1.1 and 2.0 Nightly Build (5225) - Mac 10.6.8.