Try blocks unduly catch exit commands as if they were thrown errors

[codemanyak]

I found a real bug: the exit event is unduly caught by the try block.

Originally posted by @codemanyak in #819 (comment)

[codemanyak]

There is more to it: After a try block has caught an error, consecutive errors will not be reported (though they abort the execution). This is because the try block forgot to reset a related flag on handling an error.