RS Post Settings: Use site null check instead of apiClient

Check `site == null` instead of `apiClient == null` to avoid
triggering unnecessary lazy evaluation and to match the original
guard pattern the code previously used.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: nbradbury

WordPress/src/main/java/org/wordpress/android/ui/postsrs/PostRsSettingsViewModel.kt

@@ -22,7 +22,6 @@ import org.wordpress.android.ui.postsrs.data.PostRsRestClient
 import org.wordpress.android.util.AppLog
 import org.wordpress.android.util.NetworkUtilsWrapper
 import org.wordpress.android.viewmodel.ResourceProvider
-import rs.wordpress.api.kotlin.WpApiClient
 import rs.wordpress.api.kotlin.WpRequestResult
 import uniffi.wp_api.AnyPostWithEditContext
 import uniffi.wp_api.PostEndpointType
@@ -53,7 +52,7 @@ class PostRsSettingsViewModel @Inject constructor(
 
     private val site = selectedSiteRepository.getSelectedSite()
 
-    private val apiClient: WpApiClient? by lazy {
+    private val apiClient by lazy {
         site?.let { wpApiClientProvider.getWpApiClient(it) }
     }
 
@@ -89,7 +88,7 @@ class PostRsSettingsViewModel @Inject constructor(
 
     @Suppress("TooGenericExceptionCaught")
     fun refreshPost() {
-        if (apiClient == null) return
+        if (site == null) return
         if (!networkUtilsWrapper.isNetworkAvailable()) {
             _snackbarMessages.trySend(
                 SnackbarMessage(
@@ -673,7 +672,7 @@ class PostRsSettingsViewModel @Inject constructor(
     }
 
     private fun loadPost() {
-        if (apiClient == null) return
+        if (site == null) return
         if (!networkUtilsWrapper.isNetworkAvailable()) {
             _uiState.value = PostRsSettingsUiState(
                 isLoading = false,