Bot statistics enabled by default cause performance drop, disabling them is not possible #2103
Description
If the value of parameter statistics_host is null, the following exception is thrown:
self.instance = bot(bot_id, disable_multithreading=True)
File "/usr/lib/python3/dist-packages/intelmq/lib/bot.py", line 1164, in __init__
super().__init__(bot_id=bot_id)
File "/usr/lib/python3/dist-packages/intelmq/lib/bot.py", line 239, in __init__
ttl=None,
File "/usr/lib/python3/dist-packages/intelmq/lib/cache.py", line 27, in __init__
if host.startswith("/"):
AttributeError: 'NoneType' object has no attribute 'startswith'
null should be handled gracefully (i.e. no statistics be written)