border-image: don't try to unpack values from a NULL border-image
border-image: don't try to unpack values from a NULL border-image

NULL is a valid value for border-image, so if it's NULL when unpacking,
don't try to access the struct fields, but just init the GValues for the
unpacked parameters.

bratsche/gtk-,bratsche/gtk-,jigpu/gtk,alexlarsson/gtk,Sidnioulz/SandboxGtk,Adamovskiy/gtk,Adamovskiy/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,jadahl/gtk,alexlarsson/gtk,chergert/gtk,ahodesuka/gtk,Adamovskiy/gtk,davidt/gtk,jigpu/gtk,ebassi/gtk,Lyude/gtk-,msteinert/gtk,msteinert/gtk,Distrotech/gtk2,chergert/gtk,jadahl/gtk,jessevdk/gtk,msteinert/gtk,davidt/gtk,alexlarsson/gtk,jigpu/gtk,ahodesuka/gtk,Adamovskiy/gtk,chergert/gtk,bratsche/gtk-,davidgumberg/gtk,davidgumberg/gtk,davidgumberg/gtk,ahodesuka/gtk,alexlarsson/gtk,chergert/gtk,ahodesuka/gtk,davidgumberg/gtk,jessevdk/gtk,jessevdk/gtk,grubersjoe/adwaita,msteinert/gtk,grubersjoe/adwaita,jadahl/gtk,Lyude/gtk-,jessevdk/gtk,jadahl/gtk,msteinert/gtk,ahodesuka/gtk,chergert/gtk,grubersjoe/adwaita,Distrotech/gtk2,ahodesuka/gtk,jigpu/gtk,jessevdk/gtk,ebassi/gtk,jigpu/gtk,chergert/gtk,Distrotech/gtk2,Adamovskiy/gtk,ebassi/gtk,ebassi/gtk,bratsche/gtk-,Adamovskiy/gtk,Distrotech/gtk2,Distrotech/gtk2,davidt/gtk,jigpu/gtk,jessevdk/gtk,davidgumberg/gtk,davidt/gtk,davidgumberg/gtk,Lyude/gtk-,davidt/gtk,alexlarsson/gtk,grubersjoe/adwaita,alexlarsson/gtk,Adamovskiy/gtk,Distrotech/gtk2,ebassi/gtk,jigpu/gtk,ebassi/gtk,bratsche/gtk-,Sidnioulz/SandboxGtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,Lyude/gtk-,Lyude/gtk-,alexlarsson/gtk,jadahl/gtk,Sidnioulz/SandboxGtk,jigpu/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jessevdk/gtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,davidgumberg/gtk,davidt/gtk,ahodesuka/gtk,ahodesuka/gtk,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,jadahl/gtk,alexlarsson/gtk,jadahl/gtk,chergert/gtk,msteinert/gtk,Lyude/gtk-,jadahl/gtk,Lyude/gtk-,bratsche/gtk-