Debugger may return empty stack frames while stepping

[gregg-miskelly]

Environment data

VS Code version: 1.13.1
C# Extension version: 1.10.0

Steps to reproduce

1. Debug a program. Can be anything, but something with a for loop will make it easier to reproduce.
2. Set a breakpoint and hit it
3. Start stepping rapidly

Expected behavior

Debugger should always show where you stopped

Actual behavior

Eventually the debugger will return an empty stack frame list which causes there to be no position marker, an call stack window, and an empty Variables window

Work around

Step again

Problem

The problem seems to be that sometimes VS Code will request the call stack while we are running. When this happens the debugger will correctly fail to return the call stack. But we will also cache the fact that we failed and not try again after stopping.

[gregg-miskelly]

This is fixed in the 1.12.1 version of the debugger that I am about to checkin.