The "current line" indicator disappeared when deleting spaces twice

Version Used: Visual Studio 2019 Preview 2

🔗 Originally filed as https://devdiv.visualstudio.com/DevDiv/_workitems/edit/238276

Steps to Reproduce:

1. Use the following code:

   static void Main(string[] args)
   {
       int a, b, c, d;
       a = 1;
       b = 2;
       c = 3;
       d = 4;
   }
   

2. Set a breakpoint on c = 3;

3. Start debugging and wait for the breakpoint to get hit

4. Delete the spaces before c = 3;

5. Press Ctrl+Z

6. Repeat step (4)

Expected Behavior:

The debugger still shows c = 3; as the current line (with the yellow arrow).

Actual Behavior:

After step (6), the yellow arrow goes away and the current line is now shown.