CI: fix undefined variable issue that broke windows

Author: peaBerberian

scripts/package_live_content.sh

@@ -414,6 +414,9 @@ while [[ $# -gt 0 ]]; do
   shift
 done
 
+# Exit on error, undefined variable and error in pipes
+set -euo pipefail
+
 requires_cmd printf
 requires_cmd find
 
@@ -606,6 +609,8 @@ if [[ "$(uname -s)" =~ ^(CYGWIN|MINGW|MSYS) ]]; then
 
   if [[ -n "$KEY_ID" ]]; then
     key_flag="--keys label=:key_id=$KEY_ID:key=$KEY --clear_lead 0 --protection_scheme cenc"
+  else
+    key_flag=""
   fi
 
   "$shaka_packager_cmd" \