Fix NPE in RoutingWorker after #6535 was merged

[t2gran]

Summary

We get a NullPointerException for via search after #6535 was merged. One return statement was missed when converting to use Result DTO in RoutingWorker.

Issue

🟥 There is no issue.

Unit tests

🟥 We do not have integration test on this - we probably should.

Documentation

🟥 This is a regression, no feature changes.

Changelog

🟥 The PR #6535 is in the same version as this.

Bumping the serialization version id

🟥 Not needed, no changes to model.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.24%. Comparing base (9f6be97) to head (e780290).
Report is 11 commits behind head on dev-2.x.

Files with missing lines	Patch %	Lines
...entripplanner/routing/algorithm/RoutingWorker.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #6562   +/-   ##
==========================================
  Coverage      70.24%   70.24%           
- Complexity     18381    18382    +1     
==========================================
  Files           2088     2088           
  Lines          77417    77417           
  Branches        7840     7840           
==========================================
  Hits           54380    54380           
  Misses         20265    20265           
  Partials        2772     2772           

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