util: fix segfault in UtilSignal/DisconnectSelfInHandler test case

refs #2302

Change-Id: I354c39b3ebdef2ed0f0403c15448e23856ab47b3
diff --git a/src/util/signal-signal.hpp b/src/util/signal-signal.hpp
index 6fd6c70..444c702 100644
--- a/src/util/signal-signal.hpp
+++ b/src/util/signal-signal.hpp
@@ -56,6 +56,7 @@
 
   /** \brief connects a handler to the signal
    *  \note If invoked from a handler, the new handler won't receive the current emitted signal.
+   *  \warning The handler is permitted to disconnect itself, but it must ensure its validity.
    */
   Connection
   connect(const Handler& handler);