Uploading empty file IE10/IE11 hangs indefinitely

[dolymood]

This is a bug in IE10/IE11, see uploading-empty-file-ie10-ie11-hangs-indefinitely, but i think flow.js should handle it.

[AidasK]

We can handle it, pull requests are welcome

[kalavt]

@AidasK @dolymood

with your change, when upload a empty file, event flow::fileAdded fired in chrome but not in IE10+

[AidasK]

So how should we solve it? I think ignore is better than crashed browser because of an empty file upload.

[kalavt]

if (this.fire('filesAdded', files, event)) {
    each(files, function (file) {
        if (this.opts.singleFile && this.files.length > 0) {
            this.removeFile(this.files[0]);
        }
        if ((!ie10plus || ie10plus && file.size > 0)) {
            this.files.push(file);
        }
    }, this);
}
this.fire('filesSubmitted', files, event);

@AidasK , to be consistent, fileAdded and filesAdded event need to be fire in chrome and IE,
simplely we can remove empty files from upload queue to avoid uploading empty files.