Auto merge of #314 - kbknapp:issue-277-take3, r=Vinatorul
Auto merge of #314 - kbknapp:issue-277-take3, r=Vinatorul

fix: fixes crash on invalid arg error

Once this merges I'm going to ahead and put out 1.4.5 since this fixes a crash.

Relates to #277 

Vinatorul/clap-rs,cstorey/clap-rs,kbknapp/clap-rs,Vinatorul/clap-rs,sru/clap-rs,clap-rs/clap,cstorey/clap-rs,kbknapp/clap-rs,sru/clap-rs,sru/clap-rs,cstorey/clap-rs,clap-rs/clap,clap-rs/clap,Vinatorul/clap-rs