Ensure that we skip login only when it already succeeded

Failing to do so causes a crash.

Author: hichamboushaba

WooCommerce/src/main/kotlin/com/woocommerce/android/ui/login/sitecredentials/LoginSiteCredentialsViewModel.kt

@@ -126,7 +126,8 @@ class LoginSiteCredentialsViewModel @Inject constructor(
 
     fun onContinueClick() = launch {
         loginAnalyticsListener.trackSubmitClicked()
-        if (fetchedSiteId.value != -1) {
+        val site = fetchedSiteId.value.takeIf { it != -1 }?.let { wpApiSiteRepository.getSiteByLocalId(it) }
+        if (site?.username != null) {
             // The login already succeeded, proceed to fetching user info
             fetchUserInfo()
         } else {