Resources grouping works incorrect with some data set

[chuckn0rris]

Forum post

Use the file attached to reproduce.
Resource grouping works incorrect. It shows few groups with the same name in case store was grouped after init (using store.group() method) and it throws an error if group defined in store configs. Like:

    resourceStore : {
        // fields : ['mtt'],
        sorters : [{ field : 'mtt', ascending : true }],
        groupers : [{ field : 'mtt', ascending : true }],
        data : resources
    },

app.js.zip