Do not run plymouth hook if the binary is missing.

There is a remove-boot-splash script in Mageia that can
strip plymouth from an initrd. Make this script a noop
if that has happened.

modules.d/50plymouth/plymouth-pretrigger.sh

@@ -2,6 +2,7 @@
 # -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
 # ex: ts=8 sw=4 sts=4 et filetype=sh
 
+if [ -x /bin/plymouthd ]; then
     if getargbool 1 plymouth.enable && getargbool 1 rd.plymouth -n rd_NO_PLYMOUTH; then
         [ -c /dev/null ] || mknod -m 0666 /dev/null c 1 3
         # first trigger graphics subsystem
@@ -26,3 +27,4 @@ if getargbool 1 plymouth.enable && getargbool 1 rd.plymouth -n rd_NO_PLYMOUTH; t
         # reset tty after plymouth messed with it
         [ -x /lib/udev/console_init ] && /lib/udev/console_init /dev/tty0
     fi
+fi