Potential endless loop in DashboardHost

[cactusjack66]

First of all, thanks for your great work!

I found a potential issue in the DashboardHost in the function GetNextAvailableRowColumn.
When adding the first widget, everything works fine, no matter how many visible columns there are or how wide the widget is.
But after this, when you want to add a widget that occupies more columns than are actually visible,
the functions runs into an endless loop because there is no row that has enough space for the new widget, so the application freezes.

A fix might be, to skip the check for visible columns when there is no widget in that row, like:

if (widgetAlreadyThere != null && widgetAlreadyThere.Any()) { continue; } else if (column == 0) { return new RowAndColumn(rowCount, column); }