Fix `NoSuchElementException` when using `/banner` in 1.20.5/6

[thomasmny]

Overview

Fixes Bug reported on Discord

Description

In 1.20.5, Spigot added the CraftPatternType class which is used to get an EnumBannerPatternType from the banner pattern registry using its Bukkit counterpart.

Since 1.20.5 contains experimental 1.21 patterns ("flow" & "guster") which are not present on a 1.20.5/6 server, a NoSuchElementException was thrown when attempting to get said patterns from the registry: https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/browse/src/main/java/org/bukkit/craftbukkit/block/banner/CraftPatternType.java#33

This commit attempts to catch not present patterns on startup and removes them from the allPatterns list

Checklist

• [X] I included all information required in the sections above
• [X] I tested my changes and approved their functionality
• [X] I ensured my changes do not break other parts of the code