initramfs: Prevent creating the minimal initrd if kernel was uninstalled

This condition should be a unusual, but it's possible if users are
installing kdumpst right after a kernel upgrade, without rebooting
for example. To achieve this, just check if the modules dir exists.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

initramfs/alpm-script.sh.in

@@ -15,6 +15,19 @@ if [ -n "$1" ]; then
 
 	if command -v INITRD 1>/dev/null; then
 		INITRD_installation
+
+        #  Worth noticing that it is possible (though unlikely) that during
+        #  the kdumpst package installation, users are running a previously
+        #  uninstalled kernel. Imagine if the user upgrades the kernel, and
+        #  then install kdumpst before rebooting. With that, creating an
+        #  initrd fails here since it relies on "uname -r". To prevent such
+        #  unhandled error, check if this kernel's modules directory exists.
+
+        if [ ! -d "/lib/modules/$1" ]; then
+            logger "kdumpst: no kernel modules dir; defer initrd creation to next boot"
+            exit 0
+        fi
+
 		create_initramfs_INITRD "$1"
 	fi
 	exit 0