typescript - Angular 5: Kan ikke lese egenskapen 'startsWith' av null

Når jeg kjører min Angular 5-applikasjon med kommandoen ng serve --prod, lykkes byggefasen og jeg har ingen kompileringsfeil.

Så snart jeg starter applikasjonen får jeg denne feilen:

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'startsWith' of null
    TypeError: Cannot read property 'startsWith' of null
        at t.peekStartsWith (router.js.pre-build-optimizer.js:1553)
        at t.consumeOptional (router.js.pre-build-optimizer.js:1563)
        at t.parseRootSegment (router.js.pre-build-optimizer.js:1357)
        at t.parse (router.js.pre-build-optimizer.js:1204)
        at t.applyRedirectCommands (router.js.pre-build-optimizer.js:2062)
        at t.expandRegularSegmentAgainstRouteUsingRedirect (router.js.pre-build-optimizer.js:1937)
        at t.expandSegmentAgainstRouteUsingRedirect (router.js.pre-build-optimizer.js:1887)
        at t.expandSegmentAgainstRoute (router.js.pre-build-optimizer.js:1861)
        at e.project (router.js.pre-build-optimizer.js:1798)
        at e._next (map.js.pre-build-optimizer.js:79)
        at t.peekStartsWith (router.js.pre-build-optimizer.js:1553)
        at t.consumeOptional (router.js.pre-build-optimizer.js:1563)
        at t.parseRootSegment (router.js.pre-build-optimizer.js:1357)
        at t.parse (router.js.pre-build-optimizer.js:1204)
        at t.applyRedirectCommands (router.js.pre-build-optimizer.js:2062)
        at t.expandRegularSegmentAgainstRouteUsingRedirect (router.js.pre-build-optimizer.js:1937)
        at t.expandSegmentAgainstRouteUsingRedirect (router.js.pre-build-optimizer.js:1887)
        at t.expandSegmentAgainstRoute (router.js.pre-build-optimizer.js:1861)
        at e.project (router.js.pre-build-optimizer.js:1798)
        at e._next (map.js.pre-build-optimizer.js:79)
        at D (zone.js:824)
        at D (zone.js:795)
        at zone.js:873
        at e.invokeTask (zone.js:425)
        at Object.onInvokeTask (core.js.pre-build-optimizer.js:4724)
        at e.invokeTask (zone.js:424)
        at t.runTask (zone.js:192)
        at d (zone.js:602)

Noen vet hva som kan forårsake dette? Den samme applikasjonen bygget ikke i produksjonsmodus (dvs. ng serve) fungerer feilfritt