[main] AttributeError: 'NoneType' object has no attribute 'initialize'

[devos50]

After merging #6206 I'm getting the following (silent) stack trace immediately after start when running Tribler with an empty state directory:

[PID:77036] 2021-08-12 16:23:14,110 - ERROR <ipv8_service:169> root.on_tick(): Exception occurred while trying to walk!
Traceback (most recent call last):
  File "/Users/martijndevos/Documents/tribler/src/pyipv8/ipv8_service.py", line 167, in on_tick
    strategy.take_step()
  File "/Users/martijndevos/Documents/tribler/src/pyipv8/ipv8/peerdiscovery/discovery.py", line 79, in take_step
    self.overlay.get_new_introduction()
  File "/Users/martijndevos/Documents/tribler/src/pyipv8/ipv8/community.py", line 466, in get_new_introduction
    self.bootstrap()
  File "/Users/martijndevos/Documents/tribler/src/pyipv8/ipv8/community.py", line 172, in bootstrap
    self._initialize_bootstrappers()
  File "/Users/martijndevos/Documents/tribler/src/pyipv8/ipv8/community.py", line 160, in _initialize_bootstrappers
    future = ensure_future(bootstrapper.initialize(self))
AttributeError: 'NoneType' object has no attribute 'initialize'

Possibly related to #6250. I've confirmed that I have the latest IPv8 submodule checked out.

[qstokkink]

Probably different from #6250, I suspect this line:

tribler/src/tribler-core/tribler_core/components/implementation/ipv8.py

Line 119 in 47c9b6e

community.bootstrappers.append(self.bootstrapper)

This is part of:

tribler/src/tribler-core/tribler_core/components/implementation/ipv8.py

Line 113 in 47c9b6e

def init_dht_discovery_community(self):

Which is called before initting the bootstrapper:

tribler/src/tribler-core/tribler_core/components/implementation/ipv8.py

Lines 81 to 84 in 47c9b6e

	self.bootstrapper = self.peer_discovery_community = self.dht_discovery_community = None
	self.init_dht_discovery_community()
	if not self.session.config.gui_test_mode:
	self.init_bootstrapper()

[kozlovsky]

Thanks, I was able to reproduce it on my machine, the PR should fix the problem