chunk_size must not be zero

[robfitzgerald]

problem

i ran a grid search test which used different destination coordinates. the configuration i used didn't include the grid search plugin. the rtree was unable to parse a destination vertex. the only error i received was:

[2023-11-06T15:36:58Z INFO  routee_compass::app::compass::compass_app] creating 2 parallel batches across 16 threads to run queries with chunk size 0
thread 'main' panicked at 'chunk_size must not be zero', routee-compass/src/app/compass/compass_app.rs:241:14

the error should be that "destination vertex is missing" and it should not blow up the application (error JSON response).