ci: fix updater shellcheck regression

Author: JadenJSJ

.github/workflows/ci.yml

@@ -38,6 +38,7 @@ jobs:
         continue-on-error: true
         run: |
           set -o pipefail
+          : > real-kernel.log
           sudo ./tests/integration/test_real_kernel.sh | tee real-kernel.log
 
       - name: Upload real-kernel log

lib/updater/updater.sh

@@ -282,7 +282,7 @@ updater_find_archive_member() {
   local candidate relative_path
 
   while IFS= read -r candidate; do
-    relative_path="${candidate#${unpack_dir}/}"
+    relative_path="${candidate#"${unpack_dir}"/}"
     if [[ -z "${member_regex}" || "${relative_path}" =~ ${member_regex} ]]; then
       printf '%s\n' "${candidate}"
       return 0