GtkApplication: Fix CRITICAL on shutdown when register_session=FALSE

Origin: upstream, commit:3c7d5e749ccafa75718ef00f1d5f6cdc0defacb3
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=908070
Applied-Upstream: 3.24.1

Gbp-Pq: Name GtkApplication-Fix-CRITICAL-on-shutdown-when-register_ses.patch

gtk+3.0 (3.24.0-3) unstable; urgency=medium

  * Cherry-pick 3c7d5e7 to fix a critical on gtk_application_shutdown when not
    using portals (Closes: #908070)
  * Add Applied-Upstream to last cherry-pick
  * Fix-portal-path-handling.patch: Cherry-pick from upstream.  Fix an
    incorrect dereference in the portal handling code.

[dgit import unpatched gtk+3.0 3.24.0-3]

Import gtk+3.0_3.24.0-3.debian.tar.xz

[dgit import tarball gtk+3.0 3.24.0-3 gtk+3.0_3.24.0-3.debian.tar.xz]

Import gtk+3.0_3.24.0.orig.tar.xz

[dgit import orig gtk+3.0_3.24.0.orig.tar.xz]