error Jump out of too many nested blocks needs real fix

[insignification]

Previous fix for Jump out of too many nested blocks just made it less likely to occur in some situations.
However, for large functions, when jumping out of many nested blocks it can still easily occur. (As can be seen by the very tests that "test" this behaviour - those can act as reproducible examples)
This needs a real fix.

I've opened pull request #20 , which resolves this.

[insignification]

Fix got in - can be closed now.