only clear scope vars when they were set

src/switch_core_session.c

@@ -1980,6 +1980,7 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_exec(switch_core_session_t *
 	const char *app;
 	switch_core_session_message_t msg = { 0 };
 	char delim = ',';
+	int scope = 1;
 
 	switch_assert(application_interface);
 
@@ -2010,6 +2011,7 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_exec(switch_core_session_t *
 		free(dup);
 
 		switch_channel_set_scope_variables(session->channel, &ovars);
+		scope = 1;
 	}
 
 	
@@ -2091,7 +2093,9 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_exec(switch_core_session_t *
 		switch_safe_free(expanded);
 	}
 
+	if (scope) {
 		switch_channel_set_scope_variables(session->channel, NULL);
+	}
 
 	return SWITCH_STATUS_SUCCESS;
 }