#174 Modal dialog stack

Currently if one modal dialog is open and another modal dialog is set visible an exception is thrown.
Sounds reasonable at the first glance, but there are some situations where this does not fit well:

1) "System Exception"
When system exceptions are thrown while a modal dialog is open they pull in another exception window that hides the dialog with the real error description.

2) "Modal dialog needs extra info"
If you want to outsource some infrequently needed additional input from one modal dialog to another modal dialog on top of the first this is not possible.

So why not stack modal dialogs?

Besides the two situtations mentioned above I only see one additional possiblity to open a modal dialog: Opened by a timer-task. And even in this rare case I see no problem by stacking this dialog too.