ValueError: max() iterable argument is empty - aligner_gui.py

[Gl8ching]

First, thanks for the excellent project.

I encountered a bug when using the aligner_gui.py to align one source language against multiple target languages.

STATUS: Aligning with Target 1...
STATUS: Aligning with Target 2...

during "Building multilingual alignments..." the script encounters the following error:

ValueError: max() iterable argument is empty

in aligner_gui.py changing:

    for src_indices, tgt_indices, _ in lang_alignments:
        if not src_indices:
            continue
        tgt_indices = _as_list(tgt_indices)
        src_indices = _as_list(src_indices)
        min_src = min(src_indices)

To:

    for src_indices, tgt_indices, _ in lang_alignments:
        tgt_indices = _as_list(tgt_indices)
        src_indices = _as_list(src_indices)
        if not src_indices or not tgt_indices:
            continue
        min_src = min(src_indices)

Fixed the error.