fix(chat): guard against null Component in ChatText and PlayerNameResolver

[Good627]

Problem

In commit 9278bd4, \RaidPartyTracker.checkOrRequestParty()\ was introduced to synchronize Wynntils party members by calling \PlayerNameResolver.resolve(null, m)\ with a null \Component message. This called \ChatText.resolveRealName()\ and \ChatText.flatten(message), which called \message.visit()\ without a null check, throwing an unhandled \NullPointerException\ on the render thread during \EdenModClient.onClientTick()\ and crashing the client.

Solution

• Add null-guards in \ChatText.flatten(), \ChatText.resolveRealName(), and \ChatText.resolveRealNameAnywhere()\ to return gracefully when \message == null.
• Guard \PlayerNameResolver.resolve()\ to safely fall back to \canonicalize(displayed)\ when no message component is present.
• Add unit tests in \ChatTextTest\ and \PlayerNameResolverTest\ covering null message handling.