Flutter column not expanding :(

main.dart

import 'package:flutter/material.dart';

class DemoApp extends StatelessWidget {
  Widget build(BuildContext context) => new Scaffold(body: DashboardWidget(() {
        return [
          Tab(
            text: "Goodbye!",
          )
        ];
      }));
}

void main() => runApp(new MaterialApp(home: new DemoApp()));


class DashboardWidget extends StatefulWidget {
  var _tabsProvider = () => <Widget>[];

  DashboardWidget(this._tabsProvider);

  @override
  createState() => DashboardState(_tabsProvider);
}

class DashboardState extends State<DashboardWidget> {
  var _tabsProvider = () => <Widget>[];
  var testImg =
      "https://upload.wikimedia.org/wikipedia/commons/5/59/Open-box_ballonicon2.png";
  var imageSize = 64.0;

  DashboardState(this._tabsProvider);

  @override
  Widget build(BuildContext context) {
    var tabs = _tabsProvider();
    return DefaultTabController(
      length: tabs.length,
      child: Scaffold(
        appBar: AppBar(
          title: Text("Dashboard"),
          bottom: TabBar(
            isScrollable: true,
            tabs: tabs,
          ),
        ),
        body: TabBarView(
          children: <Widget>[_createList()],
        ),
      ),
    );
  }

  Widget _createList() {
    return ListView.builder(
      itemBuilder: (context, int) => _createIssueItem(),
    );
  }

  Text boldText(String label) =>
      Text(label, style: new TextStyle(fontWeight: FontWeight.bold));

  Widget _createIssueItem() {
    createChildren() {
      return [
        Image.network(
          testImg,
          height: imageSize,
          width: imageSize,
        ),
        Padding(padding: EdgeInsets.only(left: 16.0)),
        Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            boldText("Some title"),
            Text("Address"),
            Text("Description")
          ],
        ),
      ];
    }

    return Padding(
      padding: EdgeInsets.all(8.0),
      child: Row(
        children: createChildren(),
      ),
    );
  }
}