A dumb idea, too. There's no emotional storytelling payoff in not showing what happened to Luke and Leia's mother after spending three entire movies following her maturation and adventures. When you've devoted three consecutive films in a row to telling the story of Padmé's evolution from teenaged Queen of a planet to galactic Senator and then both wife and mother of heroes it makes no sense to not depict her demise, especially when Lucas went through the trouble in the OT of mentioning that Luke never knew his real mother and Leia's memories were faint and just feelings more than anything else (man, those midichlorian-rich Force babies sense a lot in just a few short minutes after being born!) and we got the big reveal that they were twin siblings.
We knew over 30 years ago that their mother died long before the original movie. Not showing that at some point would have been extremely weak. We can quibble over how Lucas pulled off those scenes at the end of Episode III (although her state funeral on Naboo was gorgeous and I have yet to talk to anybody who didn't enjoy that), but it shouldn't even be an issue as to whether or not her fate be depicted on-screen.