shell: Fix broken indentation in shell_get_shell_surface()
shell: Fix broken indentation in shell_get_shell_surface()

Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,mchalupa/weston,giucam/weston,Fantu/compositor-spice,krezovic/weston,xorgy/weston,Gnurou/weston,Fantu/compositor-spice,eyolfson/weston,krezovic/weston,udoprog/weston,giucam/weston,Tarnyko/weston-xdg_surface_present,mchalupa/weston,jonnylamb/weston,kwm81/weston,Gnurou/weston,xorgy/weston,kwm81/weston,sir-murray/weston,sir-murray/weston,udoprog/weston,jonnylamb/weston,eyolfson/weston