Though impossible, hibernation offered under critical battery

[Alain.Cochard at unistra.fr]

Going to

Applications Menu ->
Settings ->
Power Manager ->
System (button)

I can choose 'Hibernate' for what to do 'On critical battery power'.

But when the critical power is reached, it does not hibernate.
Rather, a popup appears; it says there is not enough swap space for
hibernation to be possible.

I guess this is consistent with the fact that, when I click the
"Action Buttons", 'Hibernate' is grayed out (along with 'Hybrid
Sleep').

My point is that, if hibernation is not possible, it should not be
offered as a possible setting.

(Incidentally, I can adjust the 'Critical battery power level' to
anything between 0 and 100%, either manually or by clicking on the -/+
buttons, but I find that if I input anything above 20% it is reset to
10% after closing and coming back.)

xfce 4.16 with Fedora 34

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