boblogistics sets up that variable in on_init and on_configuration_changed so in theory, it should always exist.
However, the variable is not checked for existance upon calling the blacklist function. If Miniloaders is somehow calling that function before logistics can run it's on_init script (Which it shouldn't because it's miniloader not Miniloader, and b in boblogistics comes before m in miniloader) that could cause the error. I'm not sure why it is erroring in it's current state.
In the next version, logistics should check existance of the blacklist table (The full table tree, including bobmods, the variable it's failing on) so this shouldn't happen in future.