Linkage Checker should report clearer error when an artifact name is incorrect

Linkage Checker should report more clear error when an artifact name is incorrect. As of now, it fails with "IndexOutOfBoundsException" when a user passes invalid artifact ID:

```
Thu 14 Jan 2021 10:24:42 PM UTC: Running linkage check (validate) for beam-sdks-java-core beam-sdks-java-io-google-cloud-platform beam-runners-google-cloud-dataflow-java beam-sdks-java-io-hadoop-format sdks-java-io-kinesis sdks-java-extensions-sql-zetasql
Thu 14 Jan 2021 10:24:42 PM UTC: using baseline build/linkagecheck/baseline-sdks-java-extensions-sql-zetasql.xml
+ ./gradlew -Ppublishing -PskipCheckerFramework -PjavaLinkageArtifactIds=sdks-java-extensions-sql-zetasql -PjavaLinkageReadBaseline=build/linkagecheck/baseline-sdks-java-extensions-sql-zetasql.xml :checkJavaLinkage
Configuration on demand is an incubating feature.

> Task :checkJavaLinkage FAILED
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Exception in thread "main" java.lang.IndexOutOfBoundsException: end index (1) must not be greater than size (0)
at com.google.common.base.Preconditions.checkPositionIndexes(Preconditions.java:1420)
at com.google.common.collect.ImmutableList.subList(ImmutableList.java:433)
at com.google.cloud.tools.opensource.classpath.LinkageCheckerMain.main(LinkageCheckerMain.java:84)

FAILURE: Build failed with an exception.

```