'DQNStrategy' object has no attribute 'clock'

Hello,

I am writing to inform you that there is a problem between the avalanche-rl and DQNStrategy.
Unfortunately, in avalanche-rl when a strategy uses EWC plugin, below error will be raise:
Error for Compute EWC penalty and add it to the loss.
exp_counter = strategy.clock.train_exp_counter
if exp_counter == 0:
return
'DQNStrategy' object has no attribute 'clock'.

It needs to add 'clock' attribute in 'DQNStrategy'. I will appreciate if you update this bug in the avalanhe-rl.

avalanche-lib==0.3.1