Can not support PortID subtype: Interface name

Three switches on which the PortID subtype is Interface name are used in my experiment, and the connection between them is as follows:
switch1(GigabitEthernet1/0/1,177.0.0.104)-------(GigabitEthernet1/0/1,177.0.0.105) switch2 (GigabitEthernet1/0/2,177.0.1.105)-------(GigabitEthernet1/0/1,177.0.1.106)switch3

Firstly, I configure the SNMP protocol and LLDP protocol on three switches correctly.

Secondly, I use command snmp4sdn:readdb to read device information of the three switches, and the information is as follows:
MAC,IP,SNMP_Community,CLI_Username,CLI_Password
06:DF:44:64:01:00,177.0.0.104,public, ,
06:E4:80:8E:02:00,177.0.0.105,public, ,
78:74:6B:FE:03:00,177.0.1.106,public, ,

The result after executing this command is as follows:
MAC address (sid) IP address SNMP community CLI username CLI password
00:00:06:e4:80:8e:02:00 (7578479100416) 177.0.0.105 public
00:00:78:74:6b:fe:03:00 (132441423348480) 177.0.1.106 public
00:00:06:df:44:64:01:00 (7555994878208) 177.0.0.104 public

Thirdly, when I use command snmp4sdn:topodiscoverswitches to discovery the three switches, the error java.lang.NullPointerException occurs when executing this command.

2015-10-25 21:14:41,982 | ERROR | l for user karaf | ShellUtil | 25 - org.apache.karaf.shell.console - 3.0.3 | Exception caught while executing command
java.lang.NullPointerException
at org.opendaylight.snmp4sdn.internal.DiscoveryService.readLLDPonOneSwitch(DiscoveryService.java:1758)
at org.opendaylight.snmp4sdn.internal.DiscoveryService.readLLDPonSwitches(DiscoveryService.java:1777)
at org.opendaylight.snmp4sdn.internal.DiscoveryService.doEthSwDiscovery(DiscoveryService.java:1722)
at org.opendaylight.snmp4sdn.internal.InventoryServiceShim.doTopoDiscover(InventoryServiceShim.java:590)
at org.opendaylight.snmp4sdn.core.internal.Controller.topologyDiscoverEdges(Controller.java:482)
at org.opendaylight.snmp4sdn.core.internal.Controller.topoDiscover(Controller.java:373)
at Proxydb09afef_f7b9_4fc1_b2d9_5829eef9b60e.topoDiscover(Unknown Source)
at org.opendaylight.snmp4sdn.shell.TopoDiscoverSwitch.doExecute(TopoDiscoverSwitch.java:22)
at org.apache.karaf.shell.console.AbstractAction.execute(AbstractAction.java:33)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.karaf.shell.console.OsgiCommandSupport.execute(OsgiCommandSupport.java:39)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.karaf.shell.commands.basic.AbstractCommand.execute(AbstractCommand.java:33)[25:org.apache.karaf.shell.console:3.0.3]
at Proxy08dc5d78_0bd0_49cb_8ae2_b80fd7a0ac3b.execute(Unknown Source)[:]
at Proxy08dc5d78_0bd0_49cb_8ae2_b80fd7a0ac3b.execute(Unknown Source)[:]
at org.apache.felix.gogo.runtime.CommandProxy.execute(CommandProxy.java:78)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.Closure.executeCmd(Closure.java:477)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.Closure.executeStatement(Closure.java:403)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.Pipe.run(Pipe.java:108)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.Closure.execute(Closure.java:183)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.Closure.execute(Closure.java:120)[25:org.apache.karaf.shell.console:3.0.3]
at org.apache.felix.gogo.runtime.CommandSessionImpl.execute(CommandSessionImpl.java:92)
at org.apache.karaf.shell.console.impl.jline.ConsoleImpl.run(ConsoleImpl.java:208)
at org.apache.karaf.shell.console.impl.jline.LocalConsoleManager$2$1$1.run(LocalConsoleManager.java:109)
at java.security.AccessController.doPrivileged(Native Method)[:1.7.0_80]
at org.apache.karaf.jaas.modules.JaasHelper.doAs(JaasHelper.java:57)[26:org.apache.karaf.jaas.modules:3.0.3]
at org.apache.karaf.shell.console.impl.jline.LocalConsoleManager$2$1.run(LocalConsoleManager.java:102)[25:org.apache.karaf.shell.console:3.0.3]