Apply suggestion from @Copilot

Author: wenju-he

.github/workflows/on-push-verification-in-tree.yml

@@ -42,6 +42,10 @@ jobs:
           BRANCH="${{ github.base_ref }}"          # on: pull_request, otherwise null
           BRANCH=${BRANCH:-${{ github.ref_name }}} # on: push
           LLVM_VERSION_LONG=$(echo $BRANCH | grep -oP 'ocl-open-\K\d+') # Eg. 190 for LLVM 19
+          if [ -z "$LLVM_VERSION_LONG" ]; then
+            echo "[OPENCL-CLANG] Error: Could not parse LLVM version from branch name '$BRANCH'"
+            exit 1
+          fi
           LLVM_VERSION_SHORT=${LLVM_VERSION_LONG::-1}        # Eg. 19  for LLVM 19
           echo "llvm_version=$LLVM_VERSION_SHORT" >> $GITHUB_OUTPUT