Localization Health Bad at Outside the Map

[Zarqu0n]

https://github.com/saha-robotics/slam_toolbox/blob/60e42c3260ed8f174e5c194c56f5fd6109989031/lib/karto_sdk/src/Mapper.cpp#L1544-L1556

I think we can get data from candidateChain.size(). If robot near the scans, candidate.chain size isn't empty.