Fix `ACE_Logging_Strategy::handle_timeout` returning `-1` without releasing `ACE_Log_Msg` lock

[likema]

Before changed, there were two snippets in ACE_Logging_Strategy::handle_timeout :

if (output_file == 0)
        return -1;

whiich would return without releasing ACE_Log_Msg lock

[jwillemsen]

Don’t force push, makes it harder to review, use nullptr instead of 0

[likema]

Don’t force push, makes it harder to review, use nullptr instead of 0

OK. Shall I combine two commits into one after reviewed so that keep one issue per commit?

[jwillemsen]

No need to squash, please add/extend a unit test as reproducer