[tsparr]

I have a Save to Disk template that seems like it should work; however, is throwing an error when actually running the task. It does work successfully for books with a series, but fails on the standalones with the following error.

Traceback (most recent call last):
      File "calibre\library\save_to_disk.py", line 282, in get_path_components
      File "calibre\library\save_to_disk.py", line 247, in get_components
      File "calibre\utils\formatter.py", line 1930, in unsafe_format
      File "calibre\utils\formatter.py", line 1847, in evaluate
      File "string.py", line 194, in vformat
      File "string.py", line 203, in _vformat
    ValueError: Single '}' encountered in format string
    
    During handling of the above exception, another exception occurred:
    
    Traceback (most recent call last):
      File "calibre\gui2\save.py", line 139, in do_one_collect
      File "calibre\gui2\save.py", line 147, in collect_data
      File "calibre\library\save_to_disk.py", line 288, in get_path_components
    ValueError: Failed to calculate path for save to disk. Template: {series:'re(ifempty($,field('title') & ' - ' & field('authors')),':',' -')'}/{series:'re(ifempty($,field('title') & ' - ' & field('authors')),':',' -')'}{series_index:0>2s| - | - {title}}
    Error: Single '}' encountered in format string

The template appears as if it should work in the editor, so not sure what I'm missing.