fix npm progress pid

usr/share/install_helper.sh

@@ -202,7 +202,7 @@ pushd $TELEBIT_TMP >/dev/null
   fi
   $tmp_npm install & #>/dev/null 2>/dev/null &
   tmp_npm_pid=$!
-  while $tmp_npm_pid; do
+  while [ -n "$tmp_npm_pid" ]; do
     sleep 2
     kill -s 0 $tmp_npm_pid || tmp_npm_pid=""
     echo -n "."