Add -n to if statement checking for variable existence

Change-Id: I79e8ecbacd787600a2800fed5c66b87e1005f305

setup.sh

diff --git a/setup.sh b/setup.sh
index 9fe56c0..d2d988d 100644
--- a/setup.sh
+++ b/setup.sh
@@ -125,7 +125,7 @@
 
     local targetname="${1}"; shift
 
-    if [[ "${targetname}" ]]; then
+    if [[ -n "${targetname}" ]]; then
         _hmm "${targetname}"
         return 0
     fi