Undefined behaviour in MLD alternatives

[oxidase]

In alternativePathSearch method weighted_packed_paths is have empty paths if the middle node is also the starting node, so in debug mode there is an assertion and ub in release mode.

The issue can be reproduced with the OSM export https://www.openstreetmap.org/export#map=15/56.9103/14.5320, updated weights from crash.txt file and query curl 'http://localhost:5000/route/v1/driving/14.5303422%2C56.9087067%3B14.52962589263916%2C56.90761947631836.json?geometries=polyline&alternatives=true&steps=true&overview=full&annotations=true'

Values in the file are weights but not rates, so to reproduce the issue the line

osrm-backend/src/updater/updater.cpp

Line 192 in a53794f

const auto weight = distance_in_meters / rate;

must be changed to

        const auto weight = rate;

[oxidase]

The CSV file to reproduce the issue without updater modifications.