Bug#907950: gitg FTBFS with vala 0.42.0-1

[Adrian Bunk]

Source: gitg
Version: 3.26.0-5
Severity: serious
Tags: ftbfs

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/gitg.html

...
libgitg/gitg-diff-image-overlay.vala:24.2-24.20: error: Property `Gitg.DiffImageOverlay.alpha' with custom `get' accessor and/or `set' mutator cannot have `default' value
	public double alpha
	^^^^^^^^^^^^^^^^^^^
libgitg/gitg-diff-image-slider.vala:24.2-24.23: error: Property `Gitg.DiffImageSlider.position' with custom `get' accessor and/or `set' mutator cannot have `default' value
	public double position
	^^^^^^^^^^^^^^^^^^^^^^
libgitg/gitg-diff-view-commit-details.vala:127.2-127.25: error: Property `Gitg.DiffViewCommitDetails.use_gravatar' with custom `get' accessor and/or `set' mutator cannot have `default' value
	public bool use_gravatar
	^^^^^^^^^^^^^^^^^^^^^^^^
libgitg/gitg-diff-view-file-renderer-text.vala:99.2-99.22: error: Property `Gitg.DiffViewFileRendererText.highlight' with custom `get' accessor and/or `set' mutator cannot have `default' value
	public bool highlight
	^^^^^^^^^^^^^^^^^^^^^
libgitg/gitg-diff-view-file.vala:249.3-249.12: warning: Gtk.Menu.popup has been deprecated since 3.22
libgitg/gitg-diff-view.vala:171.2-171.25: error: Property `Gitg.DiffView.context_lines' with custom `get' accessor and/or `set' mutator cannot have `default' value
	public int context_lines
	^^^^^^^^^^^^^^^^^^^^^^^^
libgitg/gitg-progress-bin.vala:66.4-66.25: warning: Gtk.StyleContext.set_background has been deprecated since 3.18
libgitg/gitg-repository-list-box.vala:111.4-111.23: error: Property `Gitg.RepositoryListBox.Row.time' with custom `get' accessor and/or `set' mutator cannot have `default' value
			public DateTime time
			^^^^^^^^^^^^^^^^^^^^
libgitg/gitg-sidebar.vala:495.3-495.12: warning: Gtk.Menu.popup has been deprecated since 3.22
Compilation failed: 6 error(s), 3 warning(s)
make[3]: *** [Makefile:5318: libgitg_libgitg_1_0_la_vala.stamp] Error 1