I found what was causing the exception but I honestly still have no idea why it's an issue. In my MainView.axaml I have a grid and I modified the size of the RowDefinitions.

It went from this:
<Grid Name="MainGrid" ShowGridLines="True" RowDefinitions="*, 11*, 1*">

To this:
<Grid Name="MainGrid" ShowGridLines="True" RowDefinitions="*, 12*, *">

The code was apparently not happy that I tried to make the middle row bigger.