Ensure logging succeeds without run log

lib/common.sh

@@ -50,7 +50,10 @@ log() {
   local line
   line="$(timestamp) [$1] $2"
   printf '%s\n' "$line" >&2
-  [[ -n "${BACKUP_RUN_LOG:-}" ]] && printf '%s\n' "$line" >>"$BACKUP_RUN_LOG"
+  if [[ -n "${BACKUP_RUN_LOG:-}" ]]; then
+    printf '%s\n' "$line" >>"$BACKUP_RUN_LOG"
+  fi
+return 0
 }
 die() { log ERROR "$1"; exit "${2:-1}"; }