Debugging of some functions misses first debug point


For this code:
```fsharp
let TestFunction3() =
    try 
       let x = 1+1
       System.Console.WriteLine "Hello";
    with _ -> 
       System.Console.WriteLine "World"      

TestFunction3()
```
the first `try` is not laid down as a debug point.  This is caused by the debug point of the `let x` falsely replacing that of the `try` when there is no generated code in-between.




