textbuffer: Do not unset selection if failing to update the primary selection
textbuffer: Do not unset selection if failing to update the primary selection

This is expected to happen on wayland and other platforms with no primary selection,
and just leads to the selected text being cleared after any attempt to change the
text selection itself through either mouse/keyboard.

davidgumberg/gtk,jadahl/gtk,jigpu/gtk,Lyude/gtk-,jadahl/gtk,Adamovskiy/gtk,jigpu/gtk,jadahl/gtk,Lyude/gtk-,Adamovskiy/gtk,Lyude/gtk-,jessevdk/gtk,jigpu/gtk,alexlarsson/gtk,Lyude/gtk-,alexlarsson/gtk,ahodesuka/gtk,jadahl/gtk,chergert/gtk,ahodesuka/gtk,alexlarsson/gtk,grubersjoe/adwaita,jessevdk/gtk,grubersjoe/adwaita,Lyude/gtk-,Lyude/gtk-,alexlarsson/gtk,Lyude/gtk-,chergert/gtk,Adamovskiy/gtk,Adamovskiy/gtk,ahodesuka/gtk,Adamovskiy/gtk,chergert/gtk,Adamovskiy/gtk,jadahl/gtk,davidgumberg/gtk,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,ahodesuka/gtk,grubersjoe/adwaita,chergert/gtk,jadahl/gtk,jigpu/gtk,davidgumberg/gtk,ahodesuka/gtk,grubersjoe/adwaita,jessevdk/gtk,davidgumberg/gtk,grubersjoe/adwaita,ahodesuka/gtk,jigpu/gtk,Adamovskiy/gtk,ahodesuka/gtk,jessevdk/gtk,jadahl/gtk,chergert/gtk,jigpu/gtk,Lyude/gtk-,jessevdk/gtk,chergert/gtk,davidgumberg/gtk,alexlarsson/gtk,davidgumberg/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,jigpu/gtk,ahodesuka/gtk,jessevdk/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,jessevdk/gtk,alexlarsson/gtk,jigpu/gtk,Adamovskiy/gtk,chergert/gtk