[eluser]PhilTem[/eluser]
It seems that tank_auth has its own url_helper located at APPPATH . 'helpers/' that overwrites the base_url() helper and requires an argument other than the original, CI base_url() which does not provide the argument.
Now, you only need to consider the first error since the other ones are follow ups coming thereof. I'd suggest, you'd have a look at MY_url_helper and fix it to not produce errors, plus, tell the developer of tank_auth (I'm not sure if it's still actively developed) about the problem and provide a bug-fix