Failed to fetch

[Gannervi]

TypeError: Failed to fetch 
 While processing action: 
 function (dispatch, getState, api) {
    var tokens = getState().tokens.get('tokens').toJS();
    // build batch call request
    var batch = tokens.map(function (token) {
      return {
        id: token.address,
        to: token.address,
        data: tokenContract.functionToData('balanceOf', { _owner: address })
      };
    });

    return api.geth.ext.batchCall(batch).then(function (results) {
      var balances = tokens.map(function (token) {
        return {
          tokenAddress: token.address,
          amount: results[token.address].result
        };
      });

      dispatch({
        type: _actionTypes2.default.SET_TOKENS_BALANCES,
        accountId: address,
        balances: balances
      });
    });
  }