Fixed error when loading an image of a expired forwarded message(image) originated from a bot (Empty Message)

[blaize9]

I'm using tvdstaaij/telegram-history-dump to archive my chats, and when it hits a forwarded message of a bot message that has expired vysheng/tg will crash with the error below when calling tgl_do_load_photo on an ID of an Empty Message. The empty message still has the contents of the forwarded message when you request the history which is the issue causing this. This fix works seamlessly across the various clients.

Should this fix also be applied other tgl_do_load_(media type here)?

Crash on vysheng/tg when doing load_photo on an Empty Message:

SIGNAL received
hbin/telegram-cli(print_backtrace+0x2f)[0x46ef1f]
bin/telegram-cli(termination_signal_handler+0x64)[0x46efb4]
/lib/x86_64-linux-gnu/libc.so.6(+0x354a0)[0x7fbe9abd44a0]
bin/telegram-cli(tgl_do_load_photo+0x0)[0x4a0e80]
bin/telegram-cli(interpreter_ex+0x970)[0x478e50]
bin/telegram-cli[0x46f501]
/usr/lib/x86_64-linux-gnu/libevent-2.0.so.5(+0x188da)[0x7fbe9c0a38da]
/usr/lib/x86_64-linux-gnu/libevent-2.0.so.5(event_base_loop+0x7fc)[0x7fbe9c098a0c]
bin/telegram-cli(net_loop+0xa7)[0x470557]
bin/telegram-cli(loop+0x183)[0x4718c3]
bin/telegram-cli(main+0x2e5)[0x46d745]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7fbe9abbf830]
bin/telegram-cli(_start+0x29)[0x46d859]

Example of an Empty Message:

Example of an Empty Message in history:
exactly the same as a forwarded message(image)

[doubleaxe]

Hit this issue recently. Thanks for this PR. Downloaded chat log with no problem.

[tapionx]

It works! Please accept this PR @vysheng 😄

[blaize9]

Wow it's been a while since I sent this PR, glad it's still working. Hopefully @vysheng can accept it so other people won't have this issue.