handle null returning from getBlock

[zavelevsky]

Reported by licensees on other chains.
Probably the provider handles errors differently, as I've never seen this case.
In max logger verbosity I'm printing BigNumbers in readable mode and this conversion helped noticing the issue as it failed.
I believe that such a scenario in ethers over ethereum results in an earlier exception.

“related code in sdk. probably need to handle the error and do not push result to lastestBlocksMetada when error happens?”

Seems we need to check for what's returned from getBlock and getBlockNumber and handle it properly in the relevant places.