fix telnet invoke NPE #2218 (#2273)#2453

diecui1202 merged 1 commit intoapache:2.6.xapache/dubbo:2.6.xfrom

diecui1202:telnet-npe-2.6.xdiecui1202/incubator-dubbo:telnet-npe-2.6.xCopy head branch name to clipboard