enable_loop=true error

I can run d2vins with enable_loop=false successfully in single drone situation, however, when setting enable_loop=true, the process terminated by the same error @yinloonga mentioned in #1 . I think the reason is that remote_index is empty. In single drone situation, the drone will not get remote images, as a result, remote_index will be empty. It means that d2vins can not support for state estimation of single drone?

Looking forward to your reply.
@xuhao1 @Peize-Liu @yinloonga
Thanks.

@Wenminggong Thanks for your comment. D2VINS supports single drone. It's maybe a bug here.
@Peize-Liu Could you fix it by checking if ntotal==0 and return nothing in

D2SLAM/d2frontend/src/loop_detector.cpp

Line 256 in b483755

    
           int LoopDetector::queryIndexFromDatabase(const VisualImageDesc & img_desc, faiss::IndexFlatIP & index, bool remote_db,

And I found that this error appears not only in single drone case, but also in multi drones case.

Duplicate with #1
This bug has been fixed in latest commit.