[Core] Resolve null in event parsing

[Wesley-Young]

Make InfoSyncPushService and PushParamsService return empty event objects instead of base.Parse() => null!, which causes unexpected null-related exceptions.

In addition, we'd better re-consider BaseService.Parse method:

protected virtual ValueTask<TResp> Parse(ReadOnlyMemory<byte> input, BotContext context) =>
    ValueTask.FromResult<TResp>(null!);

[Copilot]

Pull Request Overview

This PR fixes null reference exceptions in event parsing by making InfoSyncPushService and PushParamsService return empty event objects instead of calling base.Parse() which returns null!.

Key changes:

• Replace base.Parse() calls with empty event object instantiation
• Prevent unexpected null-related exceptions in event handling

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
Lagrange.Core/Internal/Services/System/PushParamsService.cs	Returns new PushParamsEvent() instead of base.Parse()
Lagrange.Core/Internal/Services/System/InfoSyncPushService.cs	Returns new InfoSyncPushEvent() instead of base.Parse()

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