Wrong time output in error message

[roncapat]

Bug. Affected lines:

fuse/fuse_optimizers/src/fixed_lag_smoother.cpp

Lines 411 to 414 in 98cf1f3

	ROS_DEBUG_STREAM("The current lag expiration time is " << lag_expiration << ". The queued transaction with "
	"timestamp " << element.stamp() << " from sensor " << element.sensor_name << " has a minimum "
	"involved timestamp of " << min_stamp << ", which is " << (lag_expiration - min_stamp) <<
	" seconds too old. Ignoring this transaction.");

In my setup, I got:

The current lag expiration time is 1737452656123703516. The queued transaction with timestamp 1737452655904978711 from sensor visual_odometry has a minimum involved timestamp of 1737452655904978711, which is 218724805 seconds too old. Ignoring this transaction.

Assuming timestamps in nanoseconds, we have:

1737452656123703516
Assuming that this timestamp is in nanoseconds (1 billionth of a second):
GMT: Tuesday 21 January 2025 09:44:16.123

1737452655904978711
Assuming that this timestamp is in nanoseconds (1 billionth of a second):
GMT: Tuesday 21 January 2025 09:44:15.904

so the difference of 218724805 seconds shall be instead 0.218724805 seconds.

I can submit a PR that fixes this time scale problem when printing the time difference.