Use returned iterator from erase

Change-Id: I1ae4e4d0adc467f1bcce08fdd07a5dbf94c3111c
Reviewed-on: https://gerrit.libreoffice.org/71815
Tested-by: Jenkins
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

unoxml/source/events/eventdispatcher.cxx

@@ -69,9 +69,7 @@ namespace DOM { namespace events {
                 // erase all references to specified listener
                 if (iter->second.is() && iter->second == aListener)
                 {
-                    ListenerMap::iterator tmp_iter = iter;
-                    ++iter;
-                    rMap.erase(tmp_iter);
+                    iter = rMap.erase(iter);
                 }
                 else
                     ++iter;