Return correct alert type on malformed DH/ECDH messages.
Return correct alert type on malformed DH/ECDH messages.

In the client key exchange if the message was malformed (eg an
completely empty ECDH share) a Decoding_Error would be thrown,
then caught and a fake pre master secret generated. Move the
parsing of the message out of the try/catch block, so the correct
error is reported.

Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,webmaster128/botan,randombit/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan