Fix crash when showing MIDI regions we shouldn't.

I am not sure what causes this, but it can happen when finishing a record
sometimes.  Probably MidiSource::_writing isn't updated in the right order with
whatever triggers the redisplay, but at least not crashing is better...

1 files changed, 10 insertions, 1 deletions

diff --git a/gtk2_ardour/midi_streamview.cc b/gtk2_ardour/midi_streamview.cc
index c862a23e04..27bd465fe1 100644
--- a/gtk2_ardour/midi_streamview.cc
+++ b/gtk2_ardour/midi_streamview.cc
@@ -176,19 +176,28 @@ MidiStreamView::display_region(MidiRegionView* region_view, bool load_model)
 	}
 
 	region_view->enable_display (true);
+	region_view->set_height (child_height());
 
 	boost::shared_ptr<MidiSource> source(region_view->midi_region()->midi_source(0));
+	if (!source) {
+		error << _("attempt to display MIDI region with no source") << endmsg;
+		return;
+	}
 
 	if (load_model) {
 		source->load_model();
 	}
 
+	if (!source->model()) {
+		error << _("attempt to display MIDI region with no model") << endmsg;
+		return;
+	}
+
 	_range_dirty = update_data_note_range(
 		source->model()->lowest_note(),
 		source->model()->highest_note());
 
 	// Display region contents
-	region_view->set_height (child_height());
 	region_view->display_model(source->model());
 }