Merge pull request #4324 from jpgpi250/fix_#4322

Fix for gravity syntax error (see #4322)

gravity.sh

@@ -122,7 +122,7 @@ gravity_swap_databases() {
   gravityBlocks=$(stat --format "%b" ${gravityDBfile})
   # Only keep the old database if available disk space is at least twice the size of the existing gravity.db.
   # Better be safe than sorry...
-  if [ "${availableBlocks}" -gt "$(("${gravityBlocks}" * 2))" ] && [ -f "${gravityDBfile}" ]; then
+  if [ "${availableBlocks}" -gt "$((gravityBlocks * 2))" ] && [ -f "${gravityDBfile}" ]; then
     echo -e "  ${TICK} The old database remains available."
     mv "${gravityDBfile}" "${gravityOLDfile}"
   else