components/9990-main.sh: Fix shellcheck issue SC2236

shellcheck complains about SC2236: Use -n instead of ! -z.

Signed-off-by: Benjamin Drung <benjamin.drung@profitbricks.com>

diff --git a/components/9990-main.sh b/components/9990-main.sh
index 3fbe9bc..b50952f 100755 (executable)
--- a/components/9990-main.sh
+++ b/components/9990-main.sh
@@ -33,7 +33,7 @@ Live ()
        # Needed here too because some things (*cough* udev *cough*)
        # changes the timeout
 
-       if [ ! -z "${NETBOOT}" ] || [ ! -z "${FETCH}" ] || [ ! -z "${HTTPFS}" ] || [ ! -z "${FTPFS}" ]
+       if [ -n "${NETBOOT}" ] || [ -n "${FETCH}" ] || [ -n "${HTTPFS}" ] || [ -n "${FTPFS}" ]
        then
                if do_netmount
                then