Desktop: Fix error dialogs fail to appear in certain cases

[personalizedrefrigerator]

Summary

Prior to this pull request, calling shim.showMessageBox with only one argument (using the default second argument) resulted to an error logged to the console with no message shown. The error was caused by an attempt to access the type property on a null options object.

This error occurred when shim.showMessageBox passed null, its default options, to bridge.showMessageBox as options. In this case, the default parameter value for options of {} was not applied because JavaScript default parameters only apply if a parameter is missing or if undefined (rather than null).

shim.showMessageBox is called with one argument in cases including when deleting a folder fails.

Testing

1. Update Folder.moveToFolder to always throw.
2. Move a folder using right-click > "move to notebook".
3. Verify that an error dialog is shown.