Data editor does not show output file

[dominikbach]

Summary

When pspm_data_editor is called without options.output_file, an output file selector appears on the lower right. When options.output_file is provided in the call, the epochs are correctly saved but the output file is not shown in the data editor. This is inconsistent with options.epoch_file which is shown in the data editor when provided.

[dominikbach]

In some combinations, the epoch file selector is not shown when options.epoch_file is not provided.