--- orig/shell-tools
+++ mod/shell-tools
@@ -181,7 +181,9 @@
 	    | grep --after-context=1 --fixed-strings --line-regexp "C:${condition}" \
 	    | sed --quiet --expression='s/^A://p')
 
-	action="${action}; ${old_action}"
+	if [ -n "${old_action}" ]; then
+	    action="${action}; ${old_action}"
+	fi
     fi
     trap "${action}" "${condition}"
 }
