xwm: Check result of xcb_get_atom_name_reply
xwm: Check result of xcb_get_atom_name_reply

When printing debug information about atoms, the XWM would crash if the X
server failed to respond to a request about atom names. In practice this
occurred when the server itself crashed, e.g. when starting mplayer with the
"xv" vo.

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