Minor Bash improvements

Based on output of static analysis tool.

https://github.com/koalaman/shellcheck/wiki/SC2166
https://github.com/koalaman/shellcheck/wiki/SC2207
https://github.com/koalaman/shellcheck/wiki/SC2145
https://github.com/koalaman/shellcheck/wiki/SC2001
https://github.com/koalaman/shellcheck/wiki/SC2129
https://github.com/koalaman/shellcheck/wiki/SC2128
https://github.com/koalaman/shellcheck/wiki/SC2004
https://github.com/koalaman/shellcheck/wiki/SC2048

Closes #3162.

PiperOrigin-RevId: 160261247
diff --git a/scripts/release/common.sh b/scripts/release/common.sh
index 7cd6d0b..ca8ebd4 100755
--- a/scripts/release/common.sh
+++ b/scripts/release/common.sh
@@ -89,7 +89,7 @@
 # candidate in this release.
 function get_release_branch() {
   local branch_name=$(git_get_branch)
-  if [ -z "$(get_release_name)" -o -z "$(get_release_candidate)" ]; then
+  if [ -z "$(get_release_name)" ] || [ -z "$(get_release_candidate)" ]; then
     echo "Not a release branch: ${branch_name}." >&2
     exit 1
   fi