I get why the offline material message is there and it's a useful feature (though could be way more useful if it gave you a list of timecodes where this material is).
My issue is that I will often have a large timeline with random footage sitting on it that may/may not be online at the moment, but the final video that I will export which is sitting within the in/out points I've chosen that doesn't have any offline material still presents with this error when I go to export.
The program is obviously just looking at the whole timeline and seeing some random offline clips but it makes me nervous that maybe my final video has offline material in it (even though it doesn't).
You need to change how this works so that if in/out points are around a section that has no offline material, then there should be no error shown. In/out points should 'protect' it from errors even if the rest of the timeline is offline.