CI: Don't fail CI job when list of changed files is empty (#8066)

.github/actions/ci-incr-build-cache-save/action.yml

@@ -33,7 +33,7 @@ runs:
             -path './modules-*/files-*/*' -or \
             -path './modules-*/files-*/*' -or \
             -path './build-cache-*/*' \
-            ')' | grep -v '[.]lock$'  > ~/ci-gradle-caches-diff
+            ')' | grep -v '[.]lock$'  > ~/ci-gradle-caches-diff || true
           echo "Identified $(wc -l < ~/ci-gradle-caches-diff) changed/added files in caches/"
 
           # Only call 'tar', if there is some difference