while it's certainly not a very good example of good network citizenship to send 2 megs of NULL bytes, I think Opera shouldn't be crashing here. The fact that it does points to a bug in the code that might potentially be exploitable beyond the simple denial of service which it already is.
AFAIK Opera still runs all tabs in one shared process, so spamming one tab with 2MB of NULL will cause the whole browser (and with it all other tabs) to crash.
AFAIK Opera still runs all tabs in one shared process, so spamming one tab with 2MB of NULL will cause the whole browser (and with it all other tabs) to crash.