fix: validate.sh will failed if there are spaces in node's path

lab1/validate.sh

@@ -9,7 +9,7 @@ cd $tmp_dir
 
 rm -rf *
 cp $solution_path/*.js .
-result=$($node --test --experimental-test-coverage) ; ret=$?
+result=$($"node" --test --experimental-test-coverage) ; ret=$?
 if [ $ret -ne 0 ] ; then
   echo "[!] testing fails"
   exit 1