Custom theme fallback font error

[habamax]

I have custom theme which defines some fonts.

font:
  catalog:
    Main:
      normal: roboto-regular.ttf
      bold: roboto-bold.ttf
      italic: roboto-italic.ttf
      bold_italic: roboto-bolditalic.ttf
    Mono:
      normal: roboto-mono-regular.ttf
      bold: roboto-mono-bold.ttf
      italic: roboto-mono-italic.ttf
      bold_italic: roboto-mono-bolditalic.ttf
    Heading:
      normal: cuprum-regular.ttf
      bold: cuprum-bold.ttf
      italic: cuprum-italic.ttf
      bold_italic: cuprum-bolditalic.ttf

It works but no special symbols are rendered.

Now following the documentation I have added a fallback font:

font:
  catalog:
    Main:
      normal: roboto-regular.ttf
      bold: roboto-bold.ttf
      italic: roboto-italic.ttf
      bold_italic: roboto-bolditalic.ttf
    Mono:
      normal: roboto-mono-regular.ttf
      bold: roboto-mono-bold.ttf
      italic: roboto-mono-italic.ttf
      bold_italic: roboto-mono-bolditalic.ttf
    Heading:
      normal: cuprum-regular.ttf
      bold: cuprum-bold.ttf
      italic: cuprum-italic.ttf
      bold_italic: cuprum-bolditalic.ttf
    DroidSansFallback:
      normal: droid-sans-fallback.ttf
      bold: droid-sans-fallback.ttf
      italic: droid-sans-fallback.ttf
      bold_italic: droid-sans-fallback.ttf
  fallbacks:
    - DroidSansFallback

And asciidoctor-pdf complains:

undefined method `unpack' for nil:NilClass
   Use --trace for backtrace

And the document I try to render has only

From -> to => smth

Am I missing smth?

[habamax]

Well looks like the font I have downloaded from site pointed in the documentation is corrupted.

Using built in M+ fallback (copied from gem path) solves the issue.

[mojavelinux]

It may have had to do with how you downloaded it. I'm going to link to the file on GitHub, which I think is more approachable.