fix compilation with newer version of *mm and gcc-6.2 (RefPtr<> cast)

diff --git a/libs/canvas/wave_view.cc b/libs/canvas/wave_view.cc
index 17ee8609ff79dc641d084ea5bba29430f8a0514d..37eee914c7837433c6fc8c9ec296cb0abc909f07 100644 (file)
--- a/libs/canvas/wave_view.cc
+++ b/libs/canvas/wave_view.cc
@@ -800,7 +800,7 @@ WaveView::get_image (framepos_t start, framepos_t end, bool& full_image) const
 
                DEBUG_TRACE (DEBUG::WaveView, string_compose ("%1 CR %2 stop? %3 image %4\n", this, current_request,
                                        (current_request ? current_request->should_stop() : false),
-                                       (current_request ? current_request->image : 0)));
+                                       (current_request ? (current_request->image ? "yes" : "no") : "n/a")));
 
                if (current_request && !current_request->should_stop() && current_request->image) {