Plot hole: I never understood this... if the Good Ole Boys were running so late that the place was already closed, what would the Bunker have done if the Blues Brothers Band never showed up in the first place? There would be no band playing at all and then the amount of beer bottles being thrown around would be 100 times more than what was thrown at the Blues Brothers playing that first song. What would Bob have done with no band showing up at all? So technically the Blues Brothers saved the day.
Suggested correction: Hardly a plot hole if what they did was save the day for the bar. The original band not showing up is just really lucky for Jake and Elwood; the only thing that could have saved them doing a gig and not have the band members leave again. Without any band, the bar would probably just be more deserted, rather than full like it was.