Course api errors not handled correctly

[tkurki]

• create a route (in Freeboard)
• activate the route (in Freeboard)
• stop the server, remove the route resource file
• restart server
• reload Freeboard

Freeboard seems to still be happily navigating to the route, even if it does not exist on the server any more.

Interacting with the route navigation: forward/backward/reverse button seem like they don't do anything
...because the http requests stall and never return and on the server log there is

TypeError: Cannot read properties of undefined (reading 'geometry')
    at CourseApi.getRoutePoint (/Users/tjk/git-workspace/signalk/server/lib/api/course/index.js:773:27)
    at CourseApi.<anonymous> (/Users/tjk/git-workspace/signalk/server/lib/api/course/index.js:544:32)
    at Generator.next (<anonymous>)
    at fulfilled (/Users/tjk/git-workspace/signalk/server/lib/api/course/index.js:5:58)