checkconfig: Handle missing kernel version

src/lxc/cmd/lxc-checkconfig.in

@@ -93,6 +93,12 @@ KVER_MINOR=$($CAT $CONFIG | grep '^# Linux.*Kernel Configuration' | \
     sed -r 's/.* [0-9]\.([0-9]{1,3})\.[0-9]{1,3}.*/\1/')
 fi
 
+if [ -z "${KVER_MAJOR}" ]; then
+    echo "WARNING: Unable to detect version from configuration, assuming latest\n"
+    KVER_MAJOR="100"
+    KVER_MINOR="0"
+fi
+
 echo "--- Namespaces ---"
 echo -n "Namespaces: " && is_enabled CONFIG_NAMESPACES yes
 echo