Why do you need to catch an exception if it never occurs?
If you make the robot do:
Repeat forever
Repeat until hand is empty
find nearby tree
go to tree
use tool
end repeat
go to storage for pole
go to workbench designed to make an axe
go to storage for plank
go to workbench designed to make an axe
pick up axe
end repeat
It will never throw any error, since it will create its own axe as soon as the one its holding breaks. The setup above is also able to restart without the robot getting stuck on making a new axe, since it checks its hands first.