maint/version.sh: added quoting guards file variables

Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>

maint/version.sh

@@ -12,7 +12,7 @@ VERSION_FILE="${src_top_dir}/version.h"
 PREV_MC_VERSION="unknown"
 CURR_MC_VERSION="${PREV_MC_VERSION}"
 
-if [ -r ${VERSION_FILE} ]
+if [ -r "${VERSION_FILE}" ]
   then
     PREV_MC_VERSION=`sed -n 's/^#define MC_CURRENT_VERSION "\(.*\)"$/\1/p' "${VERSION_FILE}"`
     CURR_MC_VERSION="${PREV_MC_VERSION}"