Nightly Dotty workflow of 2023-08-05 failed

[github-actions]

See https://github.com/lampepfl/dotty/actions/runs/5768421503

[dwijnand]

Error:  Caused by: java.lang.NullPointerException
Error:  	at com.vladsch.flexmark.html.renderer.HeaderIdGenerator.generateId(HeaderIdGenerator.java:124)
Error:  	at com.vladsch.flexmark.html.renderer.HeaderIdGenerator.getId(HeaderIdGenerator.java:148)
Error:  	at dotty.tools.scaladoc.tasty.comments.markdown.SectionRenderingExtension$SectionHandler$.render(SectionRenderingExtension.scala:38)
Error:  	at dotty.tools.scaladoc.tasty.comments.markdown.SectionRenderingExtension$SectionHandler$.render(SectionRenderingExtension.scala:32)
Error:  	at com.vladsch.flexmark.html.renderer.NodeRenderingHandler.render(NodeRenderingHandler.java:16)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer$MainNodeRenderer.renderNode(HtmlRenderer.java:779)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer$MainNodeRenderer.renderChildrenNode(HtmlRenderer.java:798)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer$MainNodeRenderer.renderChildren(HtmlRenderer.java:790)
Error:  	at com.vladsch.flexmark.html.renderer.CoreNodeRenderer.render(CoreNodeRenderer.java:113)
Error:  	at com.vladsch.flexmark.html.renderer.NodeRenderingHandler.render(NodeRenderingHandler.java:16)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer$MainNodeRenderer.renderNode(HtmlRenderer.java:761)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer$MainNodeRenderer.render(HtmlRenderer.java:683)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer.render(HtmlRenderer.java:213)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer.render(HtmlRenderer.java:197)
Error:  	at com.vladsch.flexmark.html.HtmlRenderer.render(HtmlRenderer.java:230)
Error:  	at dotty.tools.scaladoc.site.TemplateFile.resolveInner(templates.scala:128)
Error:  	at dotty.tools.scaladoc.site.LoadedTemplate.resolveToHtml(LoadedTemplate.scala:54)

in publish_nightly

[dwijnand]

It didn't fail on Sunday or this morning, and we didn't merge anything in between, so it's a flaky issue.

@Florian3k are you still taking care of maintaining the scaladoc?

[Florian3k]

Yes, I'll take a look

[dwijnand]

Closing this in favour of #19524 where there are more details.