When i create a SolrCore by CoreAdmin ,a SolrException has occur

Full stack is over here:
1714364 [qtp29239443-20] ERROR org.apache.solr.core.SolrCore – org.apache.solr.common.SolrException: Error CREATEing SolrCore 'pconline_cms':
at org.apache.solr.handler.admin.CoreAdminHandler.handleCreateAction(CoreAdminHandler.java:524)
at org.apache.solr.handler.admin.CoreAdminHandler.handleRequestBody(CoreAdminHandler.java:144)
at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:135)
at org.apache.solr.servlet.SolrDispatchFilter.handleAdminRequest(SolrDispatchFilter.java:608)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:206)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:155)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1307)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:453)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:560)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1072)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:382)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1006)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:365)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:485)
at org.eclipse.jetty.server.BlockingHttpConnection.handleRequest(BlockingHttpConnection.java:53)
at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:926)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:988)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:635)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
at org.eclipse.jetty.server.BlockingHttpConnection.handle(BlockingHttpConnection.java:72)
at org.eclipse.jetty.server.bio.SocketConnector$ConnectorEndPoint.run(SocketConnector.java:264)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.solr.common.cloud.ZooKeeperException:
at org.apache.solr.core.CoreContainer.registerInZk(CoreContainer.java:853)
at org.apache.solr.core.CoreContainer.registerCore(CoreContainer.java:814)
at org.apache.solr.core.CoreContainer.register(CoreContainer.java:869)
at org.apache.solr.handler.admin.CoreAdminHandler.handleCreateAction(CoreAdminHandler.java:520)
... 30 more
Caused by: java.lang.IllegalArgumentException: Invalid path string "/collections/pconline_cms/leader_elect//election" caused by empty node name specified @39
at org.apache.zookeeper.common.PathUtils.validatePath(PathUtils.java:99)
at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1020)
at org.apache.solr.common.cloud.SolrZkClient$4.execute(SolrZkClient.java:201)
at org.apache.solr.common.cloud.SolrZkClient$4.execute(SolrZkClient.java:198)
at org.apache.solr.common.cloud.ZkCmdExecutor.retryOperation(ZkCmdExecutor.java:65)
at org.apache.solr.common.cloud.SolrZkClient.exists(SolrZkClient.java:198)
at org.apache.solr.common.cloud.ZkCmdExecutor.ensureExists(ZkCmdExecutor.java:92)
at org.apache.solr.common.cloud.ZkCmdExecutor.ensureExists(ZkCmdExecutor.java:86)
at org.apache.solr.cloud.LeaderElector.setup(LeaderElector.java:278)
at org.apache.solr.cloud.ZkController.joinElection(ZkController.java:934)
at org.apache.solr.cloud.ZkController.register(ZkController.java:757)
at org.apache.solr.cloud.ZkController.register(ZkController.java:723)
at org.apache.solr.core.CoreContainer.registerInZk(CoreContainer.java:830)
... 33 more

then ,I check the source code,I found the the base class of ShardLeaderElectionContext
do this:ZkStateReader.COLLECTIONS_ZKNODE + "/" + collection + "/leader_elect/",it create a leader_elect Zookeeper path,but throught method #setu# of class #LeaderElector# line 276, follow code are executed #String electZKPath = context.electionPath + LeaderElector.ELECTION_NODE;# ,then we have a path like this "/collections/pconline_cms/leader_elect//election"