[release] fix nullglob issue

release

@@ -9,9 +9,12 @@ err() {
 git status --porcelain | grep -q "" &&
     err "working tree is dirty, commit your changes first."
 
+# https://raimue.blog/2010/09/09/bash-for-loop-with-glob-patterns/
+shopt -s nullglob
 for file in sha256sum-*; do
     err "found $file from previous release, delete it first"
 done
+shopt -u nullglob
 
 [[ "$1" =~ ^v([0-9]+)\.([0-9]+)(\.([0-9]+))?$ ]] || \
     err "arg1 accepts the following formats: v1.0 v1.0.0"