Fix build by updating dependencies & fix panic on receiving `mimeapps.list` with lines with no handlers.

[Lehmanator]

Fixes cargo build failure from dep proc-macro2 not exposing methods before() and after() needed for feature proc_macro_span_shrink.

error[E0635]: unknown feature `proc_macro_span_shrink`
  --> /home/sam/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.52/src/lib.rs:92:30
   |
92 |     feature(proc_macro_span, proc_macro_span_shrink)
   |                              ^^^^^^^^^^^^^^^^^^^^^^

[Anomalocaridid]

Thank you!