Writing mensural impossible without --all-pages

[rettinghaus]

Describe the problem
Trying to load a Mensural MEI into Verovio and saving it back gives an Error:

[Error] MEI output with filter is not possible for mensural music

To Reproduce
Steps to reproduce the behavior:

1. Take a mensural file from Verovio's test suite
2. verovio -t mei filename
3. See error

Expected behavior
The file is written back.

Input data
See https://www.verovio.org/test-suite.xhtml?cat=mensural

Verovio information

• develop
• command-line

Environment information (as appropriate)

• macOS

[lpugin]

Looks similar to this #3804

[rettinghaus]

Ok, adding --all-pages works. But still I don't understand why. This is very counter-intuitive.
Especially as no "filter" was selected.

[lpugin]

Yes, I agree. Filters were added here

[rettinghaus]

@brdvd Could you have a look?

[rettinghaus]

Probably connected to this:
Empty measures are lost without using --all-pages. Try score-013 and score-014 from the test suite.