"assertion failed" when running mrdocs

[sdarwin]

Building mrdocs local docs, on the develop branch, adb6821

assertion failed: has_value() on line 846 in include/mrdocs/ADT/Optional.hpp

The command run was:

npx antora antora-playbook.yml --attribute branchesarray=HEAD

Results:

Extracted MrDocs-0.8.0-Linux.tar.gz to /home/jenkins/.cache/antora/reference-collector/mrdocs/linux/develop
[09:03:18.614] FATAL (antora): Command failed with exit code null: /home/jenkins/.cache/antora/reference-collector/mrdocs/linux/develop/bin/mrdocs --config=/var/lib/jenkins/workspace/mrdocs_develop/docs/mrdocs.yml --output=/home/jenkins/.cache/antora/reference-collector/reference/mrdocs/versioned/HEAD --generator=adoc --multipage=true --tagfile=reference.tag.xml

assertion failed: has_value() on line 846 in include/mrdocs/ADT/Optional.hpp

PLEASE submit a bug report to https://github.com/cppalliance/mrdocs/issues/ and include the crash backtrace.
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var LLVM_SYMBOLIZER_PATH to point to it):
0 (error) 0x00000000036ac66d
1 (error) 0x00000000036a9687
2 (error) 0x00000000037f6cc0
3 (error) 0x000000000087ae28
4 (error) 0x0000000000811920
5 (error) 0x000000000082d8f4
6 (error) 0x000000000083370a
7 (error) 0x0000000000841338
8 (error) 0x00000000007e4d39
9 (error) 0x00000000007f2719
10 (error) 0x00000000007a81c1
11 (error) 0x00000000007b9565
12 (error) 0x00000000037dd5b8
13 (error) 0x00000000037dfbc0
14 (error) 0x000000000078e825