dialer: Do not access event fields

This is needed to port to GTK+ 4 as these fields will be private.
3 jobs for event-fields in 3 minutes and 56 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #3872
librem5
build-debian-clang

00:03:53

passed #3871
librem5
build-debian-gcc

00:03:20

24.7%
passed #3873
librem5
build-debian-package

00:03:33