Die earlier if hash is NULL. (Coverity IDs 137 & 138).

ssl/s3_enc.c

@@ -231,6 +231,8 @@ int ssl3_change_cipher_state(SSL *s, int which)
 	is_exp=SSL_C_IS_EXPORT(s->s3->tmp.new_cipher);
 	c=s->s3->tmp.new_sym_enc;
 	m=s->s3->tmp.new_hash;
+	/* m == NULL will lead to a crash later */
+	OPENSSL_assert(m);
 #ifndef OPENSSL_NO_COMP
 	if (s->s3->tmp.new_compression == NULL)
 		comp=NULL;