Remove assertions that could be triggered by bad data. (#3469)

When two consecutive nodes have identical coordinates, there is no valid
bearing.  For now, make equal nodes have bearing 0.

Full fix still needs to be done via https://github.com/Project-OSRM/osrm-backend/issues/3470.

include/extractor/guidance/coordinate_extractor.hpp

@@ -28,7 +28,8 @@ class CoordinateExtractor
     /* Find a interpolated coordinate a long the compressed geometries. The desired coordinate
      * should be in a certain distance. This method is dedicated to find representative coordinates
      * at turns.
-     * Since we are computing the length of the segment anyhow, we also return it.
+     * Note: The segment between intersection and turn coordinate can be zero, if the OSM modelling
+     * is unfortunate. See https://github.com/Project-OSRM/osrm-backend/issues/3470
      */
     OSRM_ATTR_WARN_UNUSED
     util::Coordinate GetCoordinateAlongRoad(const NodeID intersection_node,