Make asm-differ more resilient to parsing errors

[ethteck]

I'm not sure how feasible it even is, but it'd be cool to have asm-differ bail on individual lines it can't handle and just fall back to some un-parsed representation, rather than totally error out

From @simonlindholm:

yes, making asm-differ more resilient would be fantastic
make it try-except the processing of every line, and do something smart in the except handler that effectively just emits a single error line

example failure: https://decomp.me/scratch/XlGeq

Requested originally by @MrSapps