mod_lcr: fix compiler warning on newer gcc

src/mod/applications/mod_lcr/mod_lcr.c

@@ -1783,7 +1783,7 @@ SWITCH_STANDARD_API(dialplan_lcr_function)
 				
 				write_data(stream, as_xml, "dialstring", current->dialstring, 2, maximum_lengths.dialstring);
 				if (as_xml) {
-					event_xml = switch_event_xmlize(current->fields, NULL);
+					event_xml = switch_event_xmlize(current->fields, "");
 					event_str = switch_xml_toxml(event_xml, SWITCH_FALSE);
 					stream->write_function(stream, event_str);
 					switch_xml_free(event_xml);

src/switch_event.c

@@ -1231,7 +1231,7 @@ SWITCH_DECLARE(switch_xml_t) switch_event_xmlize(switch_event_t *event, const ch
 		return xml;
 	}
 
-	if (fmt) {
+	if (!zstr(fmt)) {
 		va_start(ap, fmt);
 #ifdef HAVE_VASPRINTF
 		ret = vasprintf(&data, fmt, ap);