[fix](editlog) Revert BDBHA.getLeader() null check - NPE is acceptable in caller context

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

Author: dataroaring

fe/fe-core/src/main/java/org/apache/doris/ha/BDBHA.java

@@ -153,9 +153,6 @@ public List<InetSocketAddress> getElectableNodes(boolean leaderIncluded) {
     @Override
     public InetSocketAddress getLeader() {
         ReplicationGroupAdmin replicationGroupAdmin = environment.getReplicationGroupAdmin();
-        if (replicationGroupAdmin == null) {
-            return null;
-        }
         String leaderName = replicationGroupAdmin.getMasterNodeName();
         ReplicationGroup rg = replicationGroupAdmin.getGroup();
         ReplicationNode rn = rg.getMember(leaderName);