Argument Null Exception When we Try to open the particular XAML



I couldn’t able to see any flow in the Xaml. but i can able to the activities and flow in Outline Pane.
When i click the particular Flow in the outline pane, flow is getting loaded.

More over Xaml is not running even when loaded. It ended up with redeveloping my Flows.

Did any one faced such issue?

Kindly help and guide.