Crash in CreateOpenChatActivity when only using LINE Login (OpenID Connect)

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Description

I'm only using LINE Login (OpenID Connect) for user authentication —
not any of the OpenChat features.
However, my app crashes immediately with the following exception even though I never use CreateOpenChatActivity or OpenChat API:

```
Caused by java.lang.IllegalArgumentException: channel id is empty
at com.linecorp.linesdk.api.LineApiClientBuilder.(LineApiClientBuilder.java:42)
at com.linecorp.linesdk.openchat.ui.CreateOpenChatActivity$lineApiClient$2.invoke(CreateOpenChatActivity.java:32)
```

This makes it confusing for developers who only integrate LINE Login,
because this metadata is not documented or required anywhere in the LINE Login guide.

Code Example

Here’s the only part of the code where LINE SDK is used in my project:

```
class LineLoginContract : ActivityResultContract() {

override fun createIntent(context: Context, input: Unit): Intent {
val loginIntent = LineLoginApi.getLoginIntent(
context,
BuildConfig.LINE_CHANNEL_ID,
LineAuthenticationParams.Builder()
.scopes(
listOf(
Scope.PROFILE,
Scope.OPENID_CONNECT,
Scope.OC_EMAIL
)
)
.build()
)
return loginIntent
}

override fun parseResult(resultCode: Int, intent: Intent?): LineLoginResult? {
if (intent == null) return null
return LineLoginApi.getLoginResultFromIntent(intent)
}
}
```

As you can see, this only uses the LINE Login API — no reference to OpenChat, LineApiClient, or CreateOpenChatActivity.

Start with CreateOpenChatActivity.java and the LineApiClientBuilder constructor named in the stack trace. Reproduce the crash in an app using only LINE Login, then trace why the OpenChat client is initialized with an empty channel ID. Done means the LINE Login-only configuration no longer crashes while OpenChat behavior remains valid.

Written by the indexing model from the issue text.