Ensure that LemonLDAP is configured on init

This change fixes NPE regression introduced in: Id22088d62bb. Instances
which have no configuration for LemonLDAP provider are running into NPE
in init step.

Change-Id: If2cd934436cb68c710b1eb69c34aafeb04e31c81

src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
index 0da32ce..8c874e6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
@@ -131,7 +131,9 @@
     }
 
     boolean configureLemonLDAPOAuthProvider =
-        ui.yesno(true, "Use LemonLDAP OAuth provider for Gerrit login ?");
+        ui.yesno(
+            isConfigured(lemonldapOAuthProviderSection),
+            "Use LemonLDAP OAuth provider for Gerrit login ?");
     if (configureLemonLDAPOAuthProvider) {
       checkRootUrl(lemonldapOAuthProviderSection.string("LemonLDAP Root URL", ROOT_URL, null));
       configureOAuth(lemonldapOAuthProviderSection);