Hide compiler warning.
In file included from ../src/lib/grok/context.h:29,
from ../src/lib/j2k_encoder.h:36,
from ../src/lib/grok_j2k_encoder_thread.cc:5:
In member function ‘void grk_plugin::Synch::unlink()’,
inlined from ‘grk_plugin::Synch::Synch(const string&, const string&)’ at ../src/lib/grok/messenger.h:200:10:
../src/lib/grok/messenger.h:247:52: error: ‘this’ pointer is null [-Werror=nonnull]
247 | getMessengerLogger()->error("Error unlinking semaphore %s: %s", sentSemName_.c_str(),
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
248 | strerror(errno));
on Ubuntu 22.04.