Fix a potential(?) nullptr dereference

diff --git a/gtk2_ardour/fft_graph.cc b/gtk2_ardour/fft_graph.cc
index 27d5b06f3e96ddcabd70591c9745fda7a71ab8d7..25f6c6ff2943d7ae86be5e1c27bf51101e449d77 100644 (file)
--- a/gtk2_ardour/fft_graph.cc
+++ b/gtk2_ardour/fft_graph.cc
@@ -420,8 +420,6 @@ FFTGraph::draw_scales (cairo_t* cr)
 void
 FFTGraph::redraw ()
 {
-       Glib::Threads::Mutex::Lock lm  (_a_window->track_list_lock);
-
        assert (_surface);
        cairo_t* cr = cairo_create (_surface);
 
@@ -433,6 +431,8 @@ FFTGraph::redraw ()
                return;
        }
 
+       Glib::Threads::Mutex::Lock lm  (_a_window->track_list_lock);
+
        if (!_a_window->track_list_ready) {
                cairo_destroy (cr);
                queue_draw ();