Fixed "Attempt to read property on array" error in ArrayDataSource

[vvoody-]

This is fixing failing test ArrayDataSourceTest.phpt

E_WARNING: Attempt to read property "name" on array

   in src/DataSource/ArrayDataSource.php(119)
   in src/DataSource/ArrayDataSource.php(119) Tester\TestCase->{closure:Tester\TestCase::runTest():103}()
   in Cases/DataSources/BaseDataSourceTest.phpt(182) Contributte\Datagrid\DataSource\ArrayDataSource->sort()
   in src/Framework/TestCase.php(130) Contributte\Datagrid\Tests\Cases\DataSources\BaseDataSourceTest->testSort()
   in src/Framework/TestCase.php(58) Tester\TestCase->runTest()
   in Cases/DataSources/ArrayDataSourceTest.phpt(23) Tester\TestCase->run()