Build: The name does not exist in the current context

[awissu]

Hi!
I would like to publish the package for openSUSE, but bumped on problem when building rpm:

[   54s] ../lib/Manager.vala:90.23-90.44: error: The name `first_match' does not exist in the context of `Gee.TreeSet<PantheonSoundControl.Manager.Backend>'
[   54s]         var backend = s_backends.first_match ((b) => {
[   54s]                       ^^^^^^^^^^^^^^^^^^^^^^
[   54s] ../lib/Manager.vala:90.13-92.10: error: var declaration not allowed with non-typed initializer
[   54s] ../lib/Manager.vala:93.13-93.19: error: The name `backend' does not exist in the context of `PantheonSoundControl.Manager.get'
[   54s]         if (backend == null) {
[   54s]             ^^^^^^^
[   54s] ../lib/Manager.vala:94.13-94.19: error: The name `backend' does not exist in the context of `PantheonSoundControl.Manager.get'
[   54s]             backend = new Backend (in_backend);
[   54s]             ^^^^^^^
[   54s] ../lib/Manager.vala:95.29-95.35: error: The name `backend' does not exist in the context of `PantheonSoundControl.Manager.get'
[   54s]             s_backends.add (backend);
[   54s]                             ^^^^^^^
[   54s] ../lib/Manager.vala:98.16-98.22: error: The name `backend' does not exist in the context of `PantheonSoundControl.Manager.get'
[   54s]         return backend.load ();
[   54s]                ^^^^^^^
[   54s] Compilation failed: 6 error(s), 0 warning(s)

More info: https://build.opensuse.org/public/build/home:awissu:branches:X11:Pantheon/openSUSE_Tumbleweed/x86_64/pantheon-sound-control/_log

[awissu]

[  114s] ../lib/Manager.vala:90.27-90.48: error: The name `first_match' does not exist in the context of `Gee.TreeSet<SukaHottoe.Manager.Backend>'
[  114s]         Backend backend = s_backends.first_match ((b) => {
[  114s]                           ^^^^^^^^^^^^^^^^^^^^^^
[  114s] Compilation failed: 1 error(s), 0 warning(s)