fix(pd): pd raft-follower failed to get leader address due to npe (#2919)

Author: JisoLya

hugegraph-pd/hg-pd-core/src/main/java/org/apache/hugegraph/pd/raft/RaftRpcClient.java

@@ -60,7 +60,7 @@ public synchronized boolean init(final RpcOptions rpcOptions) {
     private <V> void internalCallAsyncWithRpc(final Endpoint endpoint,
                                               final RaftRpcProcessor.BaseRequest request,
                                               final FutureClosureAdapter<V> closure) {
-        final InvokeContext invokeCtx = null;
+        final InvokeContext invokeCtx = new InvokeContext();
         final InvokeCallback invokeCallback = new InvokeCallback() {
 
             @Override