Fix bug where bwt sendsd 2017 headers to electrum

[stevenroose]

It was causing this error in electrum 4.0.9:

E/i | interface.[localhost:50001] | Exception in wrapper_func: RequestCorrupted('expected 2016 headers but only got 2017')
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/electrum/util.py", line 1056, in wrapper
    return await func(*args, **kwargs)
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 481, in wrapper_func
    return await func(self, *args, **kwargs)
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 505, in run
    await self.open_session(ssl_context)
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 649, in open_session
    await group.spawn(self.monitor_connection)
  File "/usr/lib/python3.9/site-packages/aiorpcx/curio.py", line 242, in __aexit__
    await self.join()
  File "/usr/lib/python3.9/site-packages/aiorpcx/curio.py", line 211, in join
    raise task.exception()
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 703, in run_fetch_blocks
    await self._process_header_at_tip()
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 720, in _process_header_at_tip
    await self.sync_until(height)
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 729, in sync_until
    could_connect, num_headers = await self.request_chunk(height, next_height)
  File "/usr/lib/python3.9/site-packages/electrum/interface.py", line 613, in request_chunk
    raise RequestCorrupted(f"expected {size} headers but only got {res['count']}")
electrum.interface.RequestCorrupted: expected 2016 headers but only got 2017

[stevenroose]

The assertion failed without the fix.

[shesek]

Thanks!

I wonder how I never ran into this, probably only happens if the wallet is in some unusual state?