[BUG] Programmatic nested Flowcharts null in designer

## Description
I created a programmatic flowchart workflow where there are some activities which are then followed by an If statement. When viewing that workflow in the designer if I try to see the body of the if activity get a null reference error. This also happens with ForEach statements as well.

## Steps to Reproduce
create a flowchart programmatic workflow with an if activity and have the "then" attribute be a continuation of the workflow instead of just a writeline or single activity, namely it should have activties after it e.g. Event => SetVariable => If (then => ForEach( => new FlowChart( any activities)))