[BUG] InvalidFont not implements Debug, so Result<(), InvalidFont> cannot be unwrapped

[qarmin]

To Reproduce

• needs to enable in Cargo.toml featureab_glyph

  
  use crate::pdf_creator::items::data::FONT_ROBOTO_REGULAR;
  use plotters::style::register_font;
  use plotters_backend::FontStyle;

pub fn register_pdf_fonts() { register_font("roboto-regular", FontStyle::Normal, FONT_ROBOTO_REGULAR).unwrap(); }

produce error:

error[E0277]: style::font::ab_glyph::InvalidFont doesn't implement std::fmt::Debug --> src/pdf_creator/init.rs:6:77	6	register_font("roboto-regular", FontStyle::Normal, FONT_ROBOTO_REGULAR).unwrap();	^^^^^^ style::font::ab_glyph::InvalidFont cannot be formatted using {:?} because it doesn't implement std::fmt::Debug

 = help: the trait `std::fmt::Debug` is not implemented for `style::font::ab_glyph::InvalidFont`

note: required by a bound in Result::<T, E>::unwrap --> /home/rafal/.rustup/toolchains/1.72.1-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs:1072:12 | 1070 | pub fn unwrap(self) -> T | ------ required by a bound in this associated function 1071 | where 1072 | E: fmt::Debug, | ^^^^^^^^^^ required by this bound in Result::<T, E>::unwrap

**Version Information**
0.3.5