This could be a situation where we remove some account from, for example, watched account and the widget referring to that account asks for some data, but the account no longer exists. This happens because the dashboard, which also observes profile_data, has not yet removed this widget. This try-except block avoids such situations

In some cases, it happened that the parameters old_vaue and value
were passed as None, and in the meantime the data arrived. So when the
calling `first_try_callback` the result was positive, which was true
because the data had arrived. To avoid this situation, we pass
interested data as an argument to the function that checks whether the data is available
(first_try_callback), so the values and the check callback work in the same
state of the data.

Also renames now -> head_block_time because "now"
suggests more it is something like datetime.now() instead of
head block time.

things

When using:
  - calculate_current_manabar_value
  - calculate_manabar_full_regeneration_time

we observed wax error due to `now` being older than
`last_update`.

Example error:
```
WaxOperationFailedError: 10 assert_exception: Assert Exception
now >= last_update_time
```

That's caused because hived answers to batch query
in a way, blockchain state between different API calls
in that batch could change.
So we got older head block time in gdpo received by
`get_dynamic_global_properties` API
than actually was stored in rc_manabar.last_update_time taken from
`find_rc_accounts` API.