profile.linux: Start Sway on tty1 on Arch, too!

The updated profile.linux also makes sure not to "exec" sway if the
"command" command cannot find it.

.profile.linux

@@ -8,8 +8,8 @@ if [ -z  "$XDG_RUNTIME_DIR" ]; then
     export XDG_SESSION_TYPE=wayland
     export XDG_CURRENT_DESKTOP=sway
     export LIBSEAT_BACKEND=seatd
+fi
 
-    if [ -z "$WAYLAND_DISPLAY" ] && [ "$(tty)" == '/dev/tty1' ]; then
+if [ -z "$WAYLAND_DISPLAY" ] && [ "$(tty)" == '/dev/tty1' ] && command -v sway; then
     exec dbus-run-session sway -d |& tee /tmp/sway-$UID.log
 fi
-fi