[fix #10] Euen.10.sse

[fix #10] Euen.10.sse
Is `lasse_handler:notify/2` throwing an exception if `Process` is not alive?
If it is not, then you should not worry about that either. Sending a message to an inexistent process will just discard the message (exactly what you want).
On the other hand, if it does, then catch that exception instead of using `whereis` to see if the process is alive, because right after you detected it's alive, it may be dead… or right after you detected it's dead, it may come to live.