I know removing the default value will cause data binding to spit out warning messages in the debugger. Can you test and make sure we don't see the following kinds of warning messages in the debugger when info bubble shows up?

```
System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='0' BindingExpression:Path=TextFontSize; DataItem='InfoBubbleViewModel' (HashCode=22680542); target element is 'TextBox' (Name=''); target property is 'FontSize' (type 'Double')
```