top.py: Fix typo

Fix a typo in top.py that slipped in with commit 0911e53 ("httpserver: Export
thread CPU via the API").

Spotted by Nadav.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
elf: Fix SIGSEGV if dynamic table section is missing

If an ELF object does not have a dynamic table section, throw a proper
exception from _dynamic_tag() instead of faulting on nullptr.

Spotted while trying to run a static ELF binary.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>