message: [otbr-web] fix Status page exception
diff: @@ -292,7 +292,7 @@ std::string WpanService::HandleStatusRequest()
  networkInfo["IPv6:MeshLocalPrefix"] = rval;
  meshLocalPrefix = rval;
  - meshLocalPrefix.resize(meshLocalPrefix.find('/'));
  + meshLocalPrefix.resize(meshLocalPrefix.find(":/"));
  VerifyOrExit((rval = client.Execute("ipaddr")) != nullptr, ret = kWpanStatus_GetPropertyFailed);
  