[BUG] Validator unable to execute when agency_ID is missing.

Describe the bug The validator was unable to process a feed and gave an error.

To Reproduce Run the validator on the following dataset: http://transitfeeds.com/p/long-beach-transit/704/latest/download

Expected behavior No notice should be generated in this case.

Witnessed behavior Upon running the validator, I received this message before the operation ended.

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.isBlank()" because "this.agencyId" is null
    at org.mobilitydata.gtfsvalidator.domain.entity.gtfs.routes.Route$RouteBuilder.build(Route.java:281)
    at org.mobilitydata.gtfsvalidator.usecase.ProcessParsedRoute.execute(ProcessParsedRoute.java:80)
    at org.mobilitydata.gtfsvalidator.Main.lambda$main$0(Main.java:113)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at org.mobilitydata.gtfsvalidator.Main.main(Main.java:94)

Environment used

OS: macOS Catalina 10.15.6
Java version: 11.0.5
gtfs-validator version: v1.2.2

Additional context The agency_ID field only appears in the agency.txt file.

MobilityData / gtfs-validator

[BUG] Validator unable to execute when agency_ID is missing. #396