Improve Mount & Minion Handling for New Characters

[matthewhillier]

When parsing a new character, the Mounts & Minions page have no content, so the there's a silent error caught in the logs. It would be better to detect and mitigate for this rather than throw an exception.

[2020-02-26 11:24:59,503] [pool-1-thread-29] DEBUG com.ffxivcensus.gatherer.task.GathererTask - Starting evaluation of player ID: 19066937
[2020-02-26 11:24:59,753] [pool-1-thread-3] ERROR com.ffxivcensus.gatherer.task.GathererTask - Index: 0, Size: 0
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

Found during testing of #57