Submitted by pants
The function MainToken.set_mint_multisig() doesnt check that _minting_multisig doesnt equal zero before it sets it as the new minting_multisig.
This function can be invoked by mistake with the zero address as _minting_multisig, causing the system to lose its minting_multisig forever, without the option to set a new minting_multisig.
Manual code review.
Check that _minting_multisig doesnt equal zero before setting it as the new minting_multisig.
chickenpie347 (Boot Finance) confirmed 
